Aspheric Image Pickup Lens for Chromatic Aberration Correction
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Solution Overview
Problem
Existing image pickup lenses for mobile terminal devices face challenges in correcting chromatic aberration up to the peripheral region of the image plane with a small number of lenses, while maintaining high performance and small size, especially with high pixel density image pickup elements.
Innovation Solution
The image pickup lens is designed with a specific configuration comprising an aperture stop, a positive meniscus first lens, and a negative meniscus second lens, where the second lens has a concave surface on the object side and a convex surface on the image side, with an aspheric surface on the image side to enhance positive power towards the peripheral region, and specific refractive indices and Abbe's numbers are used to optimize the lens system, satisfying conditional formulas to correct aberrations and miniaturize the lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a small number of lenses are used to reduce device complexity, then chromatic aberration correction in the peripheral region deteriorates
Solution Approach 1:
The patent applies local quality by giving different surface curvatures to different regions of the lens. Specifically, the second lens has a positive curvature on its object-side surface and a negative curvature on its image-side surface, creating localized optical properties that correct chromatic aberration in the peripheral region while maintaining a simple two-lens structure. This allows effective aberration correction without increasing the number of lenses.
2Volume of moving object
If the lens system is miniaturized to reduce size, then image quality deteriorates
Solution Approach 1:
The patent employs parameter changes by optimizing the curvature radii, refractive indices, and thickness ratios of the lens elements according to specific conditional formulas. The second lens is designed with a positive curvature on the object side and a negative curvature on the image side, with curvature radius ratios satisfying 0.3 < |r2/r3| < 1.5, where r2 is the curvature radius of the object-side surface and r3 is the curvature radius of the image-side surface. These parameter optimizations enable miniaturization while maintaining high image quality and correcting chromatic aberration.
3Device complexity
If all lenses are made as positive lenses to simplify structure, then astigmatism correction becomes insufficient
Solution Approach 1:
The patent applies the inversion principle by reversing the conventional approach of using all positive lenses. Instead, the second lens is designed with a negative curvature on its image-side surface, effectively inverting the curvature sign to achieve astigmatism correction. This allows the maintenance of a simple two-lens structure while achieving sufficient astigmatism correction for high pixel density requirements.
4Manufacturing precision
If the second lens is made as a negative lens to correct astigmatism, then curvature of image field increases
Solution Approach 1:
The patent applies local quality by giving the second lens different curvature characteristics on its two surfaces. The object-side surface has a positive curvature to correct astigmatism, while the image-side surface has a negative curvature to control the image field shape. This localized differentiation of surface properties allows simultaneous achievement of astigmatism correction and reduced image field curvature, which would be impossible with a uniformly negative lens.
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
This configuration effectively corrects chromatic aberration across the image plane with a small number of lenses, achieving high performance and small size, suitable for high pixel density image pickup elements, and allows for the miniaturization of the lens system while maintaining image quality.
Implementation Method 1
the image side surface of the second lens is provided with an aspheric surface to make a positive power strong toward a lens peripheral region
Data Source
AI summary
An image pickup lens, comprises sequentially from an object side: an aperture stop, a first lens being a positive meniscus lens which has a convex surface at the object side and a concave surface at an image side opposite to the object side, and a second lens having a concave surface at the object side and an image side surface whose radius of curvature on an paraxial region is infinite or a negative value, wherein the first lens is the second lens and the image side surface of the second lens includes an aspheric surface to make a positive power strong toward a lens peripheral region, and wherein the image pickup lens is made to satisfy the following conditional formulas.1.55<n1<1.80 (1)0.4<D3/f<0.6 (2)40.0<ν2<90.0 (3)