Four-Element Lens Assembly Aberration Correction
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Solution Overview
Problem
Conventional lens assemblies for mobile phone cameras, such as triplet and four-element configurations, are insufficient for high-end imaging due to limitations in reducing chromatic aberration and total track length, and are complex to manufacture.
Innovation Solution
A compact photographing lens assembly comprising four lens elements with specific refractive powers and surface profiles, including a first positive refractive power lens, a second negative refractive power lens with aspheric surfaces, a third negative refractive power lens with a concave object-side and convex image-side surface, and a fourth negative refractive power lens with a concave image-side surface and an inflection point, along with an aperture stop between the second and first lens elements, to correct aberrations and reduce system sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional triplet or four-element lens assembly is used, then the basic imaging function is achieved, but the chromatic aberration cannot be sufficiently corrected and the total track length cannot be reduced
Solution Approach 1:
The lens assembly is divided into four distinct lens elements with specific refractive powers and surface profiles. Each element is optimized for particular aberration correction: the first element (positive refractive power) handles overall focusing, the second element (negative refractive power) corrects chromatic aberration, the third element (negative refractive power with aspheric surfaces) corrects astigmatism and field curvature, and the fourth element (negative refractive power with inflection point) corrects distortion and higher-order aberrations. This segmentation allows specialized correction functions to be distributed across multiple elements.
Solution Approach 2:
Different regions of the lens assembly have different optical properties optimized for specific functions. The first lens element has positive refractive power for overall focusing, while subsequent elements have negative refractive power specifically for aberration correction. The aspheric surfaces are strategically placed on specific elements (third and fourth elements) to address specific aberration types. This local optimization of optical properties enables comprehensive aberration correction without requiring every element to be perfectly designed for all functions.
2Manufacturing precision
If glass spherical-surface lenses are adhered together to correct chromatic aberration, then chromatic aberration is corrected, but the total track length cannot be reduced and manufacturing becomes complicated
Solution Approach 1:
The patent changes the refractive power parameters and surface profile parameters of the lens elements to achieve compactness. Specifically, the first lens element has positive refractive power while subsequent elements have negative refractive power, creating a parameter pattern that allows the principal point to be positioned far from the image plane. This parameter configuration enables the total track length to be reduced while maintaining effective chromatic aberration correction through the carefully selected refractive indices and curvatures of individual elements.
Solution Approach 2:
The patent employs aspheric surfaces on the third and fourth lens elements instead of traditional spherical surfaces. These aspheric surfaces with specific conic coefficients (k values) enable more effective correction of off-axis aberrations including astigmatism, field curvature, and distortion. The aspheric curvature allows for a more compact arrangement of lens elements while maintaining optical performance, thereby reducing the total track length without sacrificing aberration correction capability.
3Manufacturing precision
If more lens elements are added to improve image quality, then aberration correction improves, but the manufacturing process becomes more complicated
Solution Approach 1:
The lens assembly is divided into four distinct lens elements with specific refractive powers and surface profiles. Each element is optimized for particular aberration correction: the first element (positive refractive power) handles overall focusing, the second element (negative refractive power) corrects chromatic aberration, the third element (negative refractive power with aspheric surfaces) corrects astigmatism and field curvature, and the fourth element (negative refractive power with inflection point) corrects distortion and higher-order aberrations. This segmentation allows specialized correction functions to be distributed across multiple elements.
Solution Approach 2:
Different regions of the lens assembly have different optical properties optimized for specific functions. The first lens element has positive refractive power for overall focusing, while subsequent elements have negative refractive power specifically for aberration correction. The aspheric surfaces are strategically placed on specific elements (third and fourth elements) to address specific aberration types. This local optimization of optical properties enables comprehensive aberration correction without requiring every element to be perfectly designed for all functions.
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 lens assembly achieves higher resolution, reduced size, and improved image quality by effectively correcting chromatic and high-order aberrations, while simplifying the manufacturing process and reducing system sensitivity.
Implementation Method 1
a first lens element with positive refractive power having a convex object-side surface and a convex image-side surface; a second lens element with negative refractive power having a concave object-side surface and a concave image-side surface
Data Source
AI summary
This invention provides a photographing lens assembly comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface and a convex image-side surface; a second lens element with negative refractive power having a concave object-side surface and a concave image-side surface; a third lens element with negative refractive power, the object-side and image-side surfaces thereof being aspheric; a fourth lens element with negative refractive power having a concave image-side surface on which at least one inflection point is formed; and an aperture stop disposed between an imaged object and the second lens element; wherein there are four lens elements with refractive power. Such an arrangement of optical elements can effectively reduce the size of the lens assembly, attenuate the sensitivity of the optical system and enable the lens assembly to obtain higher resolution.