Six-Element Image Pickup Lens Aberration Correction
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Solution Overview
Problem
Conventional image pickup lenses with F-numbers of 2.8 or higher suffer from insufficient correction of spherical and comatic aberrations, and downsizing is hindered by longer back focus and positive refractive powers in both the front and rear groups, limiting their performance and size reduction potential.
Innovation Solution
A six-element image pickup lens configuration with a specific arrangement of lenses, including a first positive lens, a negative second lens, a third lens with variable power, a positive or negative fourth lens, a positive fifth lens, and a negative sixth lens with an aspherical image-side surface, along with conditional expressions for Abbe numbers and focal lengths to optimize refractive powers and correct aberrations, while using plastic materials for mass production and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a five-element structure image pickup lens is used to achieve higher aperture ratio, then lens speed is improved, but spherical aberration and comatic aberration correction becomes insufficient
Solution Approach 1:
The optical system is divided into multiple groups with specific refractive power assignments: front group (positive lenses) for light gathering and rear group (negative lenses) for aberration correction. This segmentation allows each group to specialize in specific functions, achieving both fast aperture ratio and proper aberration correction.
Solution Approach 2:
Different regions of the optical system have different refractive power characteristics. The front group uses positive refractive power for light collection, while the rear group uses negative refractive power for aberration correction. This local differentiation of optical properties enables simultaneous optimization of lens speed and aberration correction.
2Device complexity
If both front group and rear group are configured having positive refractive powers, then lens structure is simplified, but back focus increases and downsizing is hindered
Solution Approach 1:
Instead of using positive refractive power for both groups as in conventional designs, the invention inverts the rear group to have negative refractive power. This inversion allows the principal point to shift to the object side, shortening the back focus distance and enabling compact design without increasing structural complexity.
3Ease of manufacture
If both first lens and second lens are configured having positive refractive powers, then lens manufacturing is simplified, but color correction becomes insufficient
Solution Approach 1:
The first lens uses positive refractive power for light gathering, while the second lens uses negative refractive power for color correction. This local differentiation of refractive power signs enables effective chromatic aberration correction while maintaining manufacturing feasibility through standard lens fabrication processes.
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 configuration achieves high lens speed, corrected aberrations, and downsizing, enabling a smaller and lighter image pickup device with improved imaging quality and manufacturing efficiency, while maintaining optical performance under varying temperatures and high-temperature mounting processes.
Implementation Method 1
a first lens having a positive refractive power and comprising a convex surface directed to an object side; a second lens having a negative refractive power and comprising a concave surface directed to an image side
Implementation Method 2
the image side surface of the sixth lens comprises an aspherical shape and an inflection point at a position other than an intersection point with an optical axis
Implementation Method 3
correction of spherical aberration and comatic aberration becomes insufficient
Data Source
AI summary
There is provided an image pickup lens having a 6-element structure which has a small size and a sufficiently lens speed of F/2 or less and in which various aberrations are corrected favorably. This image pickup lens includes a first lens having a positive refractive power and comprising a convex surface directed to the object side; a second lens having a negative refractive power and comprising a concave surface directed to the image side; a third lens having a positive or negative refractive power; a fourth lens having a positive refractive power; a fifth lens having a positive refractive power and comprising a convex surface directed to the image side; and a sixth lens having a negative refractive power and comprising a concave surface directed to the image side, in this order from the object side, wherein the image side surface of the sixth lens has an aspherical shape and an inflection point at a position other than an intersection point with the optical axis, and the image pickup lens satisfies the following conditional expressions.νd1>50νd2≦30where,νd1 is an Abbe number of the first lens, andνd2 is an Abbe number of the second lens.