Aspheric Imaging Lens Aberration Correction
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Solution Overview
Problem
Conventional imaging lenses for small cameras face challenges in achieving a wide angle while maintaining high resolution and correcting aberrations, particularly due to the difficulty in balancing lens size and aberration correction, which is exacerbated by the strong refractive power required for wide angles.
Innovation Solution
The imaging lens design incorporates an object-side lens group with positive and negative refractive powers, balanced by an image-plane side lens group with specific Abbe's number ranges and curvature radii, allowing for effective aberration correction and reduced manufacturing costs through a 'positive-negative-positive' refractive power arrangement and the use of low-dispersion materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the imaging lens is reduced, then the lens becomes more compact and suitable for small cameras, but the refractive power of each lens becomes stronger making it difficult to satisfactorily correct aberrations
Solution Approach 1:
The imaging lens is divided into multiple lens elements (first lens L1, second lens L2, third lens L3, fourth lens L4, and fifth lens L5) with different refractive powers and Abbe's numbers. By segmenting the optical system into distinct elements with specific functions (positive refractive power elements for convergence, negative refractive power elements for divergence, high Abbe's number elements for chromatic aberration correction), the patent achieves effective aberration correction in a compact form factor.
2Adaptability or versatility
If a wide angle is achieved using conventional lens designs, then the imaging range is expanded, but the total length of the lens system becomes long relative to the focal length
Solution Approach 1:
The patent employs specific parameter ranges for lens curvature radii, thicknesses, and refractive powers to achieve a wide angle of view while maintaining a compact total length. The object-side surface of the first lens has a positive curvature radius within a specific range, and the aspheric coefficients are optimized to control the angle of view and total lens length, enabling a wide imaging angle without excessive system length.
3Manufacturing precision
If high-dispersion materials are used to correct field curvature and chromatic aberration of magnification, then aberration correction is improved, but manufacturing costs increase
Solution Approach 1:
The patent applies high Abbe's number materials (low dispersion) selectively to specific lens elements where they are most effective for chromatic aberration correction, rather than using them throughout the entire system. The first lens, second lens, and fourth lens are configured with high Abbe's number materials at strategic positions to correct chromatic aberration of magnification, while other elements use materials optimized for their specific functions, balancing performance and cost.
4Adaptability or versatility
If the first lens is formed with strong negative refractive power toward the lens periphery to achieve wide angle, then the angle of view is expanded, but the shape becomes difficult to manufacture with proper coating
Solution Approach 1:
The first lens is designed with an aspheric surface on its object-side, characterized by specific aspheric coefficients that provide strong negative refractive power toward the lens periphery for wide angle coverage. The aspheric shape is optimized to maintain manufacturability and proper coating applicability while achieving the required optical performance for expanding the angle of view.
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 enables a wide angle of view while satisfactorily correcting aberrations such as chromatic aberration of magnification, distortion, and field curvature, while also reducing manufacturing costs and improving image-forming performance.
Implementation Method 1
The first lens is formed in an aspheric shape so as to have strong negative refractive power toward a lens periphery from an optical axis
Implementation Method 2
the third lens and the fourth lens in the configuration are formed of high-dispersion materials. Accordingly, it is possible to correct the field curvature and the chromatic aberration of magnification
Data Source
AI summary
An imaging lens includes an object-side lens group having positive refractive power; an aperture stop; and an image plane-side lens group having positive refractive power, arranged in this order from an object side to an image plane side. The object-side lens group includes a first lens having positive refractive power; a second lens having negative refractive power; and a third lens having positive refractive power. The image plane-side lens group includes a fourth lens having positive refractive power; and a fifth lens having negative refractive power. The first lens has an aspheric shape to have negative refractive power increasing toward a lens periphery from an optical axis, and has a surface on the object side having a positive curvature radius. The first to third lenses have specific focal lengths to satisfy specific conditions. The first to fifth lenses have specific Abbe's numbers to satisfy specific conditions.