Four-Element Image Pickup Lens Aberration Correction
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Solution Overview
Problem
Conventional image pickup lenses for solid-state image sensors face challenges in downsizing while maintaining optical performance, particularly in correcting aberrations and achieving telecentricity, especially when used in mobile terminals with higher-pixel image pickup elements.
Innovation Solution
A four-element image pickup lens design comprising an aperture stop, a first positive refractive power lens, a second meniscus-shaped negative refractive power lens with a convex object-side surface, a third positive refractive power lens, and a fourth negative refractive power lens, with specific curvature radius and Abbe number conditions to correct various aberrations and achieve a short total length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the image pickup lens is downsized to meet mobile terminal requirements, then the total length and weight are reduced, but the ability to correct aberrations and achieve telecentricity deteriorates
Solution Approach 1:
The image pickup lens is divided into four distinct lens elements with specific refractive powers and shapes. Each element (first positive lens, second negative meniscus lens, third positive lens, fourth negative lens) is segmented to perform specific optical functions, allowing complex aberration correction within a compact total length by distributing optical tasks across multiple specialized components.
Solution Approach 2:
Each lens element is designed with specific local optical properties: the second lens has a meniscus shape with negative refractive power and a convex object-side surface, the fourth lens has negative refractive power, and specific curvature radius ratios are imposed on particular surfaces. These localized quality specifications enable precise control of light paths for aberration correction while maintaining compact dimensions.
2Illumination intensity
If the fourth lens is made positive (inverted Ernostar type), then the back focal length increases and principal point moves closer to image side, but the total length increases and Petzval sum correction becomes difficult
Solution Approach 1:
The patent inverts the conventional inverted Ernostar configuration by making the fourth lens negative instead of positive. This inversion allows the back focal length to be maintained at an appropriate level while reducing the total length, and simultaneously enables effective Petzval sum correction through the negative refractive power of the fourth element working in conjunction with the other lenses.
3Length of moving object
If the total lens length is shortened to achieve downsizing, then the mobile terminal size is reduced, but the angle of view becomes narrow and aberration correction becomes insufficient
Solution Approach 1:
The patent employs specific parameter relationships to achieve downsizing without sacrificing optical performance: the curvature radius of the object-side surface of the second lens is set to 0.05-0.15 times the focal length, the Abbe number of the second lens is set to 20-40, and the curvature radius ratio of specific surfaces is controlled within 0.3-1.5. These parameter changes enable compact dimensions while maintaining adequate angle of view and aberration correction for high-pixel image pickup elements.
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 design enables a smaller-sized image pickup lens with improved optical performance, including effective aberration correction and telecentricity, suitable for high-pixel image pickup elements in mobile terminals, while allowing for weight reduction and simplified manufacturing.
Implementation Method 1
a first lens having positive refractive power; a second lens having negative refractive power, whose object side surface is a convex surface; a third lens having positive refractive power; and a fourth lens having negative refractive power
Data Source
AI summary
An image pickup lens relating to the present invention is a lens for forming an image of a subject onto a photoelectric converter of a solid-state image pickup element. The image pickup lens includes, in order from an object side thereof: an aperture stop; a first lens with a positive refractive power; a second lens in a meniscus shape with a negative refractive power, whose object side surface is a convex surface; a third lens with a positive refractive power; and a fourth lens with a negative refractive power. The image pickup lens satisfies a predetermined conditions relating to a curvature radius of the object side surface of the second lens and an Abbe number of the second lens.