Five-Element Imaging Lens with Aspherical Fifth Surface
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Solution Overview
Problem
Conventional imaging lenses for small-sized image pickup apparatuses face challenges in achieving sufficient aberration correction and downsizing, with existing five-element lenses either overburdening the first few lenses with refractive power or failing to correct spherical and chromatic aberrations effectively, and having issues with pixel number increase and lens length.
Innovation Solution
A five-lens structure with a specific configuration, including a positive first lens, negative second lens, meniscus third lens, positive fourth lens, and negative fifth lens, where the first, second, and fifth lenses are fixed, and the third and fourth lenses are movable, with aspherical surfaces and curvature changing points to optimize focal length and refractive power distribution, ensuring well-corrected aberrations and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the first lens through the third lens bear almost all the refractive power, then the lens system can be simplified, but aberration correction becomes insufficient
Solution Approach 1:
The patent divides the refractive power distribution across five lenses rather than concentrating it in three. The first lens (positive), second lens (negative), third lens (positive), fourth lens (negative), and fifth lens (negative) each contribute to both focusing and aberration correction, creating a more balanced optical system that maintains simplicity while improving correction performance
Solution Approach 2:
Different lenses are assigned different refractive power characteristics tailored to their specific positions and functions. The first lens provides strong positive refractive power for focusing, while subsequent lenses with negative refractive power specifically address aberration correction at different stages of light transmission
2Length of moving object
If the overall lens length is shortened, then the image pickup apparatus can be downsized, but performance decreases due to inability to handle pixel number increase
Solution Approach 1:
The patent combines multiple functions into a compact five-lens structure where each lens serves dual purposes: the first lens handles both focusing and aberration correction, while subsequent lenses integrate image plane correction with additional aberration control, achieving high performance for increased pixel numbers within a short lens length
Solution Approach 2:
The patent optimizes refractive indices, curvatures, and spacing parameters of the five lenses to achieve the desired balance between compact length and performance. By carefully selecting material properties and geometric parameters, the system maintains high imaging quality despite the reduced overall length
3Ease of manufacture
If the front group is made to have spherical surfaces, then manufacturing is easier, but spherical aberration and comatic aberration are not sufficiently corrected
Solution Approach 1:
The patent employs aspherical surfaces on specific lenses (particularly the first and third lenses) to correct spherical and comatic aberrations. These aspherical surfaces provide the necessary optical path correction while remaining compatible with modern manufacturing techniques, achieving superior aberration control compared to purely spherical surfaces
4Device complexity
If both front group and rear group have positive refractive powers, then the lens structure is simplified, but the principal point position shifts and back focus becomes longer
Solution Approach 1:
The patent creates an asymmetric refractive power distribution where the first and third lenses have positive power while the second, fourth, and fifth lenses have negative power. This asymmetric configuration allows the principal point to be positioned optimally and controls the back focus length, achieving compact design without excessive back focus requirements
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 proposed lens structure achieves well-corrected aberrations, compact size, and reduced lens length, enabling smaller and higher-performance image pickup apparatuses and portable terminals while maintaining effective focusing and minimizing environmental impact.
Implementation Method 1
a first lens having positive refractive power, a second lens having a negative refractive power; a third lens having a positive refractive power; a fourth lens having a negative refractive power; and a fifth lens having negative refractive power
Data Source
AI summary
Provided is an imaging lens, and also provided are an image pickup apparatus and a portable terminal both equipped with the imaging lens. The imaging lens includes in order: a positive first lens having a convex object-side surface; a negative second lens having a concave image-side surface; a negative meniscus-shaped third lens having a convex object-side surface; a positive fourth lens having a convex image-side surface; and a negative fifth lens having a concave image-side surface. The image-side surface of the fifth lens is aspherical and has an inflection point at a position of the optical axis. The third and the fourth lenses are integrally moved to focus, and the following conditional relation is satisfied: 0.75<f34/f<1.30, where f34 is the combined focal length of the third lens and the fourth lens, and f is the focal length of the entire system of the imaging lens.