Wide-Angle Imaging Lens with Segmented Front and Rear Groups
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Solution Overview
Problem
Imaging lenses used in digital cameras and surveillance cameras face challenges in being compact with a small F-number and wide angle of view, while also needing to handle high pixel counts and correct for spherical aberration and large incident light ray angles.
Innovation Solution
The design consists of a front group and a rear group of lenses, with specific configurations and cemented lenses to achieve a wide angle of view, reduced overall lens length, and improved optical performance, including conditional expressions for lens parameters such as Abbe numbers and focal lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the lens system uses a conventional configuration to achieve wide angle of view, then the angle of view is improved, but the overall lens length becomes too long
Solution Approach 1:
The lens system is divided into a front group and a rear group separated by an aperture stop. The front group includes a first lens (negative meniscus) and a second lens (positive), while the rear group includes a third lens (positive) and a fourth lens (negative). This segmentation allows each group to be optimized independently for wide angle of view while maintaining compact overall length through controlled separation distance.
Solution Approach 2:
The patent employs a retrofocus configuration where the first lens from the object side has negative refractive power, creating a virtual image at a position closer to the object than the actual object. This dimensional rearrangement of light paths allows the lens to achieve wide angle of view without requiring a proportionally long physical length, effectively decoupling the traditional relationship between focal length and lens length.
2Length of stationary object
If the lens system is designed for compact size, then the overall lens length is reduced, but spherical aberration becomes under-corrected
Solution Approach 1:
Each lens element is designed with specific local optical properties: the first lens uses negative meniscus shape with particular curvature radii (R1, R2) to control spherical aberration; the second lens uses positive refractive power with specific Abbe number (νAr2) to correct chromatic aberration; the third and fourth lenses are configured to further refine spherical and coma aberrations. This localized optimization of optical quality at each element level enables compact design while maintaining high aberration correction.
Solution Approach 2:
The patent specifies precise parameter ranges for each lens element including refractive indices (n), curvature radii (R), thicknesses (D), and Abbe numbers (ν). By optimizing these parameters within defined ranges and satisfying specific conditional expressions, the system achieves compact length while correcting spherical aberration to acceptable levels for high pixel count sensors.
3Manufacturing precision
If the lens system uses more lenses to improve optical performance, then aberration correction is improved, but the device complexity increases
Solution Approach 1:
Each lens element is designed to perform multiple functions simultaneously. For example, the first negative meniscus lens not only provides the necessary negative refractive power for retrofocus configuration but also contributes to spherical aberration correction and controls the light cone angle. The second positive lens corrects chromatic aberration while maintaining the wide angle of view. This multi-functionality reduces the need for additional dedicated correction elements.
Solution Approach 2:
The patent combines aberration correction functions into the existing lens elements rather than adding separate correction elements. The negative meniscus shape of the first lens, the specific refractive index and Abbe number of the second lens, and the configuration of the third and fourth lenses work together to correct multiple aberrations simultaneously, merging correction functions into the primary imaging path.
4Measurement precision
If the lens system is optimized for high pixel count sensors, then resolution is improved, but the incident angle of light rays at peripheral angles becomes too large
Solution Approach 1:
The lens system is designed to dynamically control the light cone angle at the image plane through its optical configuration. The negative meniscus first lens and the specific arrangement of positive and negative lenses in the rear group work together to compress the light cone angle for peripheral rays, ensuring that even at wide angles of view, the incident angles at the image plane remain within acceptable ranges for high pixel count sensors.
Solution Approach 2:
The aperture stop positioned between the front and rear groups acts as an intermediary element that controls the light cone geometry. It limits the maximum angle of rays reaching the rear group and helps manage the incident angles at the image plane, preventing excessive angles that would occur with simple wide angle configurations while maintaining the wide field of view needed for high pixel count resolution.
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 solution provides an imaging lens with a wide angle of view, reduced overall lens length, small F-number, and suppressed light ray incident angle, suitable for high pixel count image sensors, achieving high optical performance and correcting various aberrations.
Implementation Method 1
the first and the second lenses from the object side in the front group are a negative meniscus lens with a convex surface on the object side and a negative lens respectively
Data Source
AI summary
An imaging lens consisting of a front group, a stop, and a rear group. The first and the second lenses from the object side in the front group are a negative meniscus lens with a convex surface on the object side and a negative lens respectively. The first and the second lenses from the image side in the front group are both positive lenses. The rear group is composed of a positive lens, a negative lens, and one or more positive lenses disposed in order from the object side. If the maximum total angle of view when an object at infinity is in focus is taken as 2ω, the imaging lens satisfies a conditional expression, 2ω>130°.