Compact Image Lens with Aspherical Second Element for Aberration Correction
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Solution Overview
Problem
Conventional image-capturing lenses for mobile devices face challenges in reducing size and weight while effectively correcting aberrations such as spherical aberration, off-axis coma aberration, and astigmatism, especially with advancements in pixel resolution.
Innovation Solution
A 3-lens configuration comprising a meniscus-shaped first lens with positive power near the optical axis, an aspherical second lens with positive power near the axis and negative power in the periphery, and a meniscus-shaped third lens with convex and concave surfaces, optimized by specific conditional expressions to reduce total length and correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a positive-negative-negative power arrangement is employed, then size reduction is achieved, but spherical aberration and off-axis coma aberration are inadequately corrected and F-number cannot be reduced
Solution Approach 1:
The second lens is designed with aspherical shape and differentiated power distribution: positive power near the optical axis and negative power in the periphery. This local quality variation enables effective correction of both spherical aberration (from paraxial rays) and off-axis coma aberration (from marginal rays) simultaneously, resolving the contradiction between compact size and aberration correction performance.
2Length of stationary object
If a positive-positive-negative configuration is employed, then total length reduction is achieved, but off-axis coma aberration and astigmatism are inadequately corrected
Solution Approach 1:
The aspherical second lens with position-dependent power (positive at axis, negative at periphery) provides localized correction capabilities that address both on-axis spherical aberration and off-axis coma/astigmatism simultaneously, maintaining compact total length while improving aberration correction.
3Volume of moving object
If size reduction is achieved, then compactness is improved, but off-axis aberration cannot be well corrected and F-number cannot be reduced
Solution Approach 1:
The aspherical second lens introduces spatially varying power distribution where the periphery has negative power to correct off-axis coma aberration while the axis has positive power for spherical aberration correction. This local differentiation enables effective off-axis aberration correction in a compact lens design.
Solution Approach 2:
The aspherical surface of the second lens provides curvature variation that differs from simple spherical surfaces. This aspherical curvature enables simultaneous control of spherical aberration (paraxial) and off-axis coma aberration (marginal), achieving compact size with improved off-axis correction performance.
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 enables a compact image-capturing lens that well-corrects aberrations, reduces size and weight, and maintains excellent telecentric characteristics, suitable for high-resolution image sensors in mobile devices.
Implementation Method 1
a first lens of a meniscus shape with a positive power near an optical axis... a second lens of an aspherical shape with a positive power near the optical axis and a negative power in a periphery... a third lens of a meniscus shape
Data Source
AI summary
An image-capturing lens includes, in order from an object side: a meniscus-shaped first lens which has positive power near an optical axis; a second lens which has positive power near the optical axis and has negative power in the periphery of the second lens; and a meniscus-shaped third lens. The image-capturing lens satisfies the following conditional formulas: TL/f<1.10, 2.00<(r2+r1)/(r2−r1)<4.00, and 0.07<D2/f<0.19, where TL: the air-converted distance from the object-side surface of the first lens to the image-side surface thereof, f: the focal length of the entire system, r2: the radius of curvature of the first lens on the image side thereof, r1: the radius of curvature of the first lens on the object side thereof, D2: the distance between the first lens and the second lens.