Four-Lens Imaging System with Aspheric Fourth Lens
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Solution Overview
Problem
Existing imaging lenses face challenges in accommodating increased pixel density, maintaining compact size, and achieving high performance while minimizing chromatic aberration and manufacturing sensitivity, particularly with concave surfaces on negative lenses which can lead to image surface variations.
Innovation Solution
A four-lens imaging lens system comprising a positive first lens, a negative meniscus second lens, a positive meniscus third lens, and an aspheric fourth lens with a concave surface near the optical axis, optimized for focal lengths and Abbe numbers to ensure telecentricity, reduce chromatic aberration, and enhance manufacturing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the object side surface of the second lens is made concave to achieve telecentric characteristic, then the telecentric performance is improved, but the manufacturing sensitivity increases and image surface varies easily
Solution Approach 1:
The patent inverts the conventional configuration by placing the concave surface on the image side instead of the object side of the negative lens. This inversion maintains the telecentric characteristic while significantly reducing manufacturing sensitivity and image surface variation.
Solution Approach 2:
The patent changes the geometric parameters of the negative lens by specifying that the concave surface be on the image side, and optimizes curvature radii and thickness to balance telecentric performance with manufacturing stability.
2Manufacturing precision
If more lenses are added to cope with increased pixel density, then the imaging performance is improved, but the lens size and complexity increase
Solution Approach 1:
The patent optimizes the parameters of each lens element, particularly using aspheric surfaces on the fourth lens and carefully selecting curvature radii and Abbe numbers, to achieve high imaging performance with only four lenses rather than requiring more elements.
Solution Approach 2:
The patent uses lenses with different Abbe numbers (vd1 > 50, vd2 > 30) to achieve chromatic aberration correction, effectively combining materials with different optical properties to enhance performance without adding more lens elements.
3Manufacturing precision
If the aperture stop is disposed on the object side to secure telecentric characteristic, then the telecentric performance is improved, but the lens system becomes more sensitive to manufacturing variations
Solution Approach 1:
The patent inverts the approach by configuring the negative lens with the concave surface on the image side, which inherently provides telecentric characteristic without requiring the aperture stop to be positioned at the extreme object side, thereby reducing manufacturing sensitivity.
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 system effectively corrects longitudinal chromatic aberration, lateral color, and field curvature, while maintaining a compact size and improving manufacturing aptitude by optimizing lens materials, surface shapes, and power distributions, ensuring high performance and reduced image surface variation.
Implementation Method 1
both surfaces of the fourth lens are aspheric and the fourth lens has a concave surface on the image side in a vicinity of an optical axis of the fourth lens. The imaging lens satisfies formulae (1) to (4): vd1>50, vd2>30, |f2/f1|>1, and 0.51
Implementation Method 2
both surfaces of the fourth lens are aspheric and the fourth lens has a concave surface on the image side in a vicinity of an optical axis of the fourth lens
Implementation Method 3
a second lens of a negative lens in a meniscus shape having a concave surface on an image side thereof
Implementation Method 4
a first lens of a positive lens having a convex surface on the object side thereof; a second lens of a negative lens in a meniscus shape having a concave surface on an image side thereof; a third lens of a positive lens in a meniscus shape having a convex surface on the image side thereof
Data Source
AI summary
An imaging lens is provided and has, in order from the object side, a first lens of a positive lens having a convex surface on the object side thereof; a second lens in a meniscus shape having a concave surface on an image side thereof; a third lens in a meniscus shape having a convex surface on the image side thereof; and a fourth lens of a positive or negative lens, both surfaces of the fourth lens being aspheric and the fourth lens having a concave surface on the image side and in a vicinity of an optical axis of the fourth lens. The Abbe numbers of the first and second lenses as well as the focal distances of the first to fourth lenses satisfies specific conditions.