Imaging Lens Aberration Correction via Segmented Groups
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Solution Overview
Problem
Current imaging lenses for document reading face challenges in achieving a small F-number, high resolution, and a wide angle of view while minimizing size, particularly when used with high-definition imaging devices, as they often fail to adequately correct aberrations and have insufficient angle of view for large document images.
Innovation Solution
The design incorporates a specific configuration of lenses, including a first meniscus lens with a concave object-side surface, a second positive lens, a third negative meniscus lens with a convex image-side surface, and a fourth lens with a convex object-side surface, arranged in a specific order to satisfy conditional expressions that optimize the lens system's performance, including a distance ratio between lenses and lens shapes that enhance aberration correction and reduce size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the focal length of the imaging lens is reduced to decrease the conjugate length and reduce apparatus size, then the angle of view increases, but various aberrations become insufficiently corrected
Solution Approach 1:
The imaging lens is divided into multiple lens groups (first lens group with positive refractive power, second lens group with negative refractive power, third lens group with positive refractive power) to independently control and correct different types of aberrations while maintaining a compact focal length
Solution Approach 2:
Each lens group is designed with specific refractive power characteristics tailored to correct particular aberrations - the first group handles spherical aberration, the second group handles chromatic aberration, and the third group fine-tunes field curvature, allowing optimized local performance throughout the system
2Measurement precision
If the F-number is reduced to increase light gathering capability and resolution, then the aperture diameter increases, but the lens size and weight increase
Solution Approach 1:
The lens system uses a telecentric configuration where the optical axis is extended through the aperture stop, allowing dynamic adjustment of the effective aperture while maintaining a compact physical lens size and F-number optimization
3Area of stationary object
If the angle of view is increased to capture large document images, then the focal length must be reduced, but this causes insufficient aberration correction
Solution Approach 1:
The lens system is segmented into three distinct lens groups, each responsible for correcting specific aberrations that arise from wide-angle imaging, allowing the system to maintain both large field of view and high optical precision
Solution Approach 2:
The lens groups are designed with specific refractive power parameters and glass material properties optimized for wide-angle imaging, with the second lens group having a negative refractive power ratio that specifically addresses field curvature and distortion in wide-field applications
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 allows for an imaging lens with a small F-number, high resolution, and a wide angle of view, effectively addressing the limitations of existing lenses by improving aberration correction and reducing the overall size of the lens system, enabling high-definition imaging with a compact form factor.
Implementation Method 1
an imaging lens suitable as a reading lens for reading a document image... the imaging lens used for reading the document image needs to effectively correct various aberrations such as field curvature and distortion
Data Source
AI summary
Disclosed is an imaging lens having a small F-number, high resolution, a sufficiently wide angle of view, and a small size. An imaging lens includes: a first lens with a meniscus shape having a concave surface facing an object side; a second positive lens; a third negative lens with a meniscus shape having a convex surface facing an image side; and a fourth lens having a convex surface facing the object side. The first to fourth lenses are arranged in this order from the object side. The imaging lens satisfies the following conditional expression: 0.25<D/f<4.0 (where D indicates the distance between the first lens and the second lens on the optical axis and f indicates the focal length of the entire system).