Imaging Lens Aberration Correction via Aspheric Inflection Point
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Solution Overview
Problem
Image pickup systems face challenges in forming clear images due to issues like shading, where the peripheral portions of images are darkened due to unadjusted chief ray angles, leading to spherical aberration, comatic aberration, and astigmatism.
Innovation Solution
An imaging lens module comprising a first positive-powered meniscus lens, a second negative-powered meniscus lens with stronger power than the first and third lenses, and a third positive-powered lens with an aspheric inflection point on its image-side surface, which adjusts the chief ray angle to 25° or less, ensuring even light distribution and correcting aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional lens designs are used, then the lens structure is simple, but image shading occurs due to unadjusted chief ray angles
Solution Approach 1:
The third lens incorporates an aspheric surface with an inflection point specifically on its image-side surface, creating local geometric variation to adjust chief ray angles. This localized aspheric design modifies light distribution in the peripheral regions without requiring complete redesign of all lens surfaces, thereby improving illumination uniformity while maintaining reasonable structural complexity.
Solution Approach 2:
The aspheric inflection point on the image-side surface of the third lens introduces controlled curvature variation to optimize the chief ray angle distribution. This curved surface design enables precise control over light ray paths, ensuring even light distribution across the image sensor while avoiding the need for additional corrective optical elements.
2Adaptability or versatility
If the chief ray angle is increased to expand field of view, then the angle of view increases, but spherical aberration, comatic aberration, and astigmatism worsen
Solution Approach 1:
The aspheric inflection point is positioned specifically on the image-side surface of the third lens to locally modify ray convergence characteristics. This localized geometric feature corrects spherical aberration, comatic aberration, and astigmatism in the peripheral field regions without compromising the overall field of view, enabling high-angle imaging with improved aberration control.
Solution Approach 2:
The lens design employs specific parameter relationships, including the second lens having stronger power than the first and third lenses, and the third lens having a positive focal length within a specific range. These parameter optimizations, combined with the aspheric inflection point, enable the system to maintain aberration correction precision even when imaging at high chief ray angles up to 25 degrees or more.
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 effectively inhibits image shading by ensuring even light distribution across the image sensor, correcting spherical aberration, comatic aberration, and astigmatism, while maintaining a compact lens design.
Implementation Method 1
a third lens having positive (+) power and an inflection point on an imaging surface thereof facing an image side... which adjusts the chief ray angle to 25° or less
Implementation Method 2
correcting spherical aberration, comatic aberration, and astigmatism
Data Source
AI summary
Disclosed is an imaging lens. The imaging lens includes a first lens having positive (+) power, a second lens having negative (−) power, and a third lens having positive (+) power and an inflection point on an imaging surface thereof facing an image side, wherein the first to third lenses are sequentially arranged from an object, and the second lens has power stronger than power of the first and third lenses.