Four-Lens Imaging Optical System Aberration Correction
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Solution Overview
Problem
Existing imaging optical systems face challenges in correcting various aberrations while achieving miniaturization, particularly in wide-angle views, due to issues with curvature, refractive power distribution, and sensitivity to assembly errors.
Innovation Solution
A four-lens imaging optical system with specific refractive power configurations, including a second lens element with a surface position at the maximum effective diameter on the object side and a fourth lens element with an inflection point, satisfies conditions that correct spherical and chromatic aberrations while minimizing system length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the first lens element has a large curvature portion (small curvature radius) facing the object side, then the angle of view is widened, but it becomes difficult to correct comma aberration or chromatic aberration
Solution Approach 1:
The invention changes the curvature radius parameter of the first lens element to a specific range (|RS1| > 0.5f) to balance wide angle of view with aberration correction. This parameter optimization allows the system to achieve both wide angle capability and acceptable aberration levels without requiring extreme curvature values.
Solution Approach 2:
The invention uses a composite lens structure where the first lens element is combined with subsequent lens elements having specific refractive powers and dispersion characteristics. The fourth lens element with high Abbe number (ν4 > 50) compensates for chromatic aberration introduced by the strongly curved first element, while the overall four-lens configuration corrects coma and other off-axis aberrations.
2Length of stationary object
If the refractive power of the first lens element is extremely strong, then the focal length is shortened, but error sensitivity becomes extremely high and performance variation increases during assembly
Solution Approach 1:
The invention optimizes the refractive power parameter of the first lens element by constraining its curvature radius to |RS1| > 0.5f, preventing excessively strong power. This parameter control reduces sensitivity to manufacturing and assembly errors while maintaining compact focal length through the coordinated design of all four lens elements.
Solution Approach 2:
The invention divides the total optical power into four separate lens elements with alternating positive and negative refractive powers. This segmentation distributes the optical burden, preventing any single element from having extreme refractive power that would cause high error sensitivity, while achieving the desired compact focal length through the cumulative effect of all elements.
3Length of stationary object
If the imaging lens is miniaturized, then the total length is reduced, but it becomes difficult to correct various aberrations
Solution Approach 1:
The invention introduces aspherical surfaces on key lens elements (first, second, and fourth elements) that provide dynamic aberration correction capability. The aspherical profiles allow the lens to correct coma, spherical aberration, and other off-axis errors more effectively within a compact form factor, as the varying curvature compensates for optical path differences without requiring increased lens length.
Solution Approach 2:
The invention employs a composite optical system combining spherical and aspherical lens elements with specifically selected refractive indices and Abbe numbers. The fourth lens element with high Abbe number (ν4 > 50) and aspherical surface provides simultaneous correction of chromatic and monochromatic aberrations, enabling miniaturization without sacrificing aberration correction performance.
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 various aberrations, secures telecentricity, and achieves miniaturization, enabling the use of high-pixel imaging elements in compact devices like mobile phones.
Implementation Method 1
the refractive power (optical power) of the first lens element is extremely strong. This may make error sensitivity extremely high, and may increase the performance variation at the time of assembling into an imaging lens
Implementation Method 2
an imaging device using such an imaging element have been widely spread. There is also an increasing demand for miniaturization and high performance of an imaging optical system (imaging lens) for forming an optical image of an object on a light receiving surface
Data Source
AI summary
An imaging optical system, an imaging device, and a digital apparatus have a four lens construction with positive, negative, positive, and negative refractive powers. A surface position at the maximum effective diameter of the second lens element is located on the object side than a surface vertex thereof. The fourth lens element has an inflection point at a position other than the intersection of the optical axis and the fourth lens element. The optical system satisfies the following conditions.0.7<f1/f<5−0.8<(RS1+RS2)/(RS1−RS2)<3−3<(RS3+RS4)/(RS3−RS4)<20.03<d2/TL<0.22W>72ν4>50, and0.55<Y/TL<0.8where f1 is a focal length of the first lens element, f is a focal length of the entire optical system, RS1, RS3, RS2, RS4 are curvature radii of the object-side surface and the image-side surface of the first and second lens elements, d2 is an optical axis distance between the first and second lens elements, TL is a total length of the entire optical system, W is a maximum half angle of view, ν4 is an Abbe number of the fourth lens element, and Y is a maximum image height.