Aspheric Two-Lens Imaging System for Compact Track Length
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Solution Overview
Problem
Conventional imaging lens systems for compact electronic products face challenges in achieving a balance between image quality and total track length, with two-lens element systems suffering from defocus issues due to wavelength disparities and three-lens element systems being unsuitable for compact designs due to excessive length.
Innovation Solution
A two-non-cemented lens element imaging system with a positive first lens element and a negative second lens element, both having aspheric surfaces, where the second lens element's image-side surface changes from concave to convex, and specific relations between Abbe numbers, curvature radii, and focal lengths are maintained to optimize focusing performance and reduce total track length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a two-lens element optical system is used, then the total track length is reduced for compact design, but excessive difference between focuses of short and long wavelengths occurs causing defocus
Solution Approach 1:
The patent applies parameter changes by carefully selecting the Abbe numbers of the two lens elements (V1 and V2) to satisfy specific mathematical relationships. By controlling the dispersion parameters (Abbe numbers) and curvature radii of the lens surfaces, the system achieves both compact size and corrected chromatic aberration. The aspheric surface parameters are also optimized to balance the focusing performance across different wavelengths while maintaining a short total track length.
2Manufacturing precision
If a three-lens element optical system is used, then image quality is improved, but the total track length becomes excessively long for compact products
Solution Approach 1:
The patent applies local quality by giving each lens element specific local characteristics - the first lens element has a convex object-side surface and convex or flat image-side surface, while the second lens element has a concave object-side surface and concave image-side surface. Both surfaces are aspheric with specifically designed curvature distributions. This localized optimization of each element's shape and refractive properties allows the two-element system to achieve image quality comparable to three-element systems while maintaining compact dimensions.
3Ease of manufacture
If conventional two-lens element systems are used, then the structure is simple and manufacture cost is reduced, but unfavorable image quality occurs due to defocus
Solution Approach 1:
The patent applies spheroidality by designing aspheric surfaces for all lens elements. The aspheric profiles are defined by specific mathematical equations with optimized coefficients that control the curvature distribution across each surface. This curved surface design enables the two-lens system to correct chromatic aberration and improve focusing performance across the field of view, achieving image quality that would otherwise require more complex multi-element systems, while maintaining relatively simple manufacturing processes for aspheric lenses.
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 provides improved image quality by balancing focusing performance across short and long wavelengths while minimizing the total track length, making it suitable for compact electronic products.
Implementation Method 1
a positive first lens element having a convex object-side surface at a paraxial region thereof and a convex or flat image-side surface at the paraxial region thereof; a negative second lens element having a concave object-side surface at a paraxial region thereof and a concave image-side surface at a paraxial region thereof
Implementation Method 2
both the object-side and image-side surfaces being aspheric; wherein, the shape of the image-side surface of the second lens element changes from concave when near an optical axis to convex when away from the optical axis
Data Source
AI summary
This invention provides an imaging lens system comprising two non-cemented lens elements with refractive power: a positive first lens element having a convex object-side surface at a paraxial region and a convex or flat image-side surface at the paraxial region; and a negative second lens element having a concave object-side surface at a paraxial region and a concave image-side surface at a paraxial region, and both the object-side and image-side surfaces being aspheric; wherein, the shape of the image-side surface of the second lens element changes from concave when near an optical axis to convex when away from the optical axis. By such arrangement, the imaging lens system has not only a shorter total track length for compact electronic products, but also the advantage of a more comparable focusing performance between the short wavelength and long wavelength applications with improved image quality.