Compact Imaging Lens with Rear-Group Aberration Control
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Solution Overview
Problem
Existing imaging devices with high-pixel solid-state imaging elements face challenges in reducing the total length of imaging lenses while maintaining optical performance, as further reduction in total length leads to insufficient correction of distortion aberration, coma aberration, and field curvature, making it difficult to achieve size and thickness reduction while ensuring high optical performance.
Innovation Solution
An imaging lens configuration with a front-group having positive refractive power and a rear-group having negative refractive power, where the rear-group lens surface is concave near the optical axis and convex on the periphery, optimized to intentionally generate distortion aberration within a predetermined range, allowing for total length reduction while balancing other aberrations, and a computing device corrects the distortion aberration to maintain optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the total length of the imaging lens is further reduced, then the size and thickness of the imaging device are reduced, but distortion aberration, coma aberration, and field curvature are not corrected sufficiently
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, and third lens group with positive refractive power). Each group is responsible for correcting specific types of aberrations, allowing the system to maintain high optical performance in a compact form factor.
Solution Approach 2:
Each lens group is designed with specific refractive power and aberration correction characteristics tailored to its position in the optical system. The first lens group primarily corrects spherical aberration, the second lens group corrects coma aberration and field curvature, and the third lens group corrects distortion aberration, creating localized optimization throughout the system.
2Length of stationary object
If lenses with center thickness and edge thickness close to process limit are employed, then thickness reduction is achieved, but mass productivity becomes extremely difficult
Solution Approach 1:
The lens design specifies optimal thickness ranges for each lens group that balance miniaturization with manufacturability. By pre-defining these parameters within feasible process limits, the design enables standard manufacturing processes to produce high-quality lenses at scale without requiring extreme or custom fabrication techniques.
3Length of stationary object
If a single focus lens is used due to size limitations, then the imaging device size is reduced, but high optical performance with wide angle of view becomes difficult to achieve
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, and third lens group with positive refractive power). Each group is responsible for correcting specific types of aberrations, allowing the system to maintain high optical performance in a compact form factor.
Solution Approach 2:
The patent describes a focus adjustment mechanism that moves the second lens group (with negative refractive power) along the optical axis to achieve focus from infinity to close-up distances. This dynamic adjustment capability allows the compact multi-group lens system to maintain high optical performance across different focus distances, something a fixed single-focus lens could not achieve.
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 enables the reduction of imaging device size and thickness while maintaining favorable optical performance, achieving a wide-angle, small imaging lens with improved optical performance by balancing aberrations and correcting distortion aberration effectively.
Implementation Method 1
a front-group lens system having positive refractive power, and a rear-group lens system having negative refractive power
Implementation Method 2
an imaging element that converts an optical image formed on an image forming surface by the imaging lens, into an electric signal
Data Source
AI summary
An imaging device of the disclosure includes an imaging lens; an imaging element that converts an optical image formed on an image forming surface by the imaging lens, into an electric signal; and a computing device that corrects distortion aberration of an image picked up by the imaging element. The imaging lens includes, in order from object side, a front-group lens system having positive refractive power, and a rear-group lens system having negative refractive power, a lens surface on a closest side to the image of the rear-group lens system being concave on an image side near an optical axis and convex on the image side around a periphery, and the following conditional expression is satisfied:5(%)<ODMax<20(%) (1)where ODMax is a maximum value of distortion aberration within an imaging region of the imaging lens.