Imaging Lens with Aspheric Surfaces for Compact Design
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Solution Overview
Problem
Current imaging lenses in mobile terminals face challenges in achieving a low-profile design with high brightness and a wide angle of view while effectively correcting various aberrations, particularly due to limitations in F-number and total track length.
Innovation Solution
The imaging lens configuration consists of three lens groups (seven lenses) with specific refractive power arrangements and aspheric surfaces, including a first lens group with positive refractive power, a second lens group with positive composite focal length, and a third lens group with negative refractive power, optimized to shorten the total track length and correct chromatic aberrations, spherical aberrations, and astigmatism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of lenses is increased to correct various aberrations and improve imaging performance, then the imaging quality and aberration correction are improved, but the total track length increases making the device thicker
Solution Approach 1:
The lens system is divided into three distinct lens groups (first lens group with positive refractive power, second lens group with positive composite focal length, and third lens group with negative refractive power) that can be optimized independently. This segmentation allows each group to contribute specifically to aberration correction while maintaining a compact overall structure, resolving the contradiction between using more lenses for better correction and keeping the total track length short.
Solution Approach 2:
Multiple lenses are arranged in a nested configuration where the first, second, and third lens groups are positioned sequentially with optimized spacing. The aspheric surfaces of individual lenses are designed to work together in a nested manner, allowing seven lenses to be packed efficiently within a short total track length while maintaining effective aberration correction across the entire system.
2Illumination intensity
If the F-number is reduced to provide high brightness, then the brightness is improved, but the angle of view becomes narrower and aberration correction becomes more difficult
Solution Approach 1:
Aspheric surfaces are applied selectively to specific lens surfaces (object-side surface of the first lens, image-side surface of the second lens, and object-side surface of the third lens) rather than uniformly to all surfaces. This local application of aspheric geometry allows optimal control of light rays at different zones, enabling both wide angle of view and high brightness while effectively correcting spherical aberration and other monochromatic aberrations that typically worsen at low F-numbers.
3Illumination intensity
If the F-number is reduced to provide high brightness, then the brightness is improved, but the aberration correction becomes more difficult
Solution Approach 1:
The lens system uses a composite design combining spherical and aspheric surfaces across different lens groups. The first lens group uses aspheric surfaces for strong aberration control, the second lens group uses aspheric surfaces for fine-tuning, and the third lens group provides negative power with aberration correction. This composite approach allows effective aberration correction at low F-number (Fno ≤ 2.0) while maintaining high brightness, overcoming the typical trade-off where low F-number makes aberration correction extremely difficult.
4Length of stationary object
If the total track length is shortened to achieve a low-profile design, then the device thickness is reduced, but the ability to correct aberrations and provide wide angle of view deteriorates
Solution Approach 1:
The lens system employs significant parameter changes through aspheric surface geometry defined by specific mathematical equations with multiple coefficients (A4, A6, A8, A10, A12, A14, A16). These parameter changes in surface shape allow the lenses to correct multiple types of aberrations simultaneously within a short total track length, achieving both compact form factor and high imaging performance that would normally require a much longer optical path.
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 results in a low-profile design with an F-number of 2.0 or less, providing high brightness and a wide angle of view of 70 degrees or more, while effectively correcting aberrations, and allows for mass production using plastic materials at a lower cost.
Implementation Method 1
a first lens with positive refractive power having a convex object-side surface and a second lens with negative refractive power having a concave image-side surface near the optical axis which are arranged in order from the object side
Implementation Method 2
a third lens and a fourth lens each having at least one aspheric surface which are arranged in order from the object side
Data Source
AI summary
An imaging lens in which a positive (refractive power) first lens group, positive second lens group, and negative third lens group are arranged in order from the object side to the image side. The first lens group includes a positive first lens having a convex object-side surface and a negative second lens having a concave image-side surface near the optical axis. The second lens group includes third and fourth lenses each having at least one aspheric surface. The third lens group includes a negative fifth lens having a concave object-side surface near the axis, a positive sixth lens having a convex image-side surface near the axis, and a negative seventh lens having a concave image-side surface near the axis. The lenses are not joined to each other and the seventh lens has an aspheric image-side surface whose shape changes from concave to convex as the distance from the axis increases.