Zoom Lens Abbe Number Ratio for Chromatic Aberration Control
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Solution Overview
Problem
Current zoom lens systems for small-sized imaging devices, such as digital cameras and surveillance cameras, face challenges in minimizing aberrations across the entire image area, especially when transitioning between visible and near-infrared ray regions, and require a smaller F-number to achieve clear images in low light conditions.
Innovation Solution
A three-group zoom lens system is designed with a first lens group having negative refractive power, a second lens group with positive refractive power, and a third lens group also with positive refractive power, where the first and second lens groups move along the optical axis for zooming and focusing, with specific Abbe number and focal distance ratios to minimize chromatic aberration and provide a smaller F-number, allowing for high-resolution imaging from visible to near-infrared regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the imaging device area and pixel number are increased to attain high-resolution imaging, then the imaging resolution is improved, but the optical system size increases and aberrations increase
Solution Approach 1:
The optical system is divided into three distinct lens groups with different refractive powers (negative, positive, positive). Each group is optimized for specific functions: the first group for chromatic aberration correction, the second for zooming and focusing, and the third for additional aberration control. This segmentation allows high-resolution imaging without proportionally increasing the overall optical system volume.
2Measurement precision
If the imaging device area and pixel number are increased to attain high-resolution imaging, then the imaging resolution is improved, but the aberrations of the focused light increase
Solution Approach 1:
Different lens groups are assigned specific optical properties to address different types of aberrations locally. The first lens group with negative refractive power specifically targets chromatic aberration correction, while the second and third groups with positive refractive power handle spherical aberration and field curvature. This localized optimization of optical properties across the imaging area reduces overall aberrations while maintaining high resolution.
Solution Approach 2:
The patent employs composite lens structures including doublet lenses (combinations of two lenses with different Abbe numbers) and aspherical surfaces. These composite optical elements combine materials and geometries with different properties to correct multiple types of aberrations simultaneously, enabling high-resolution imaging across the entire image area.
3Illumination intensity
If the F-number is reduced to obtain clear images in low light conditions, then the light gathering ability is improved, but the aberration correction becomes more difficult
Solution Approach 1:
The second lens group is designed to move along the optical axis during zooming and focusing operations. This dynamic adjustment capability allows the system to maintain optimal aberration correction across different focal lengths and object distances, even when operating at lower F-numbers for improved light gathering in surveillance and night photography 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
The system effectively reduces chromatic aberration and focus distortion across the entire image area, enabling high-resolution imaging both day and night with reduced noise, even in low light conditions, and supports a zoom ratio of 3.5 to 4, providing clear images with a smaller F-number.
Implementation Method 1
a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, wherein the first lens group, the second lens group, and the third lens group are sequentially disposed from an object side to an image plane side along an optical axis of the zoom lens system
Implementation Method 2
the sixth lens and the tenth lens may each include an aspherical surface, respectively
Data Source
AI summary
A zoom lens system according to an example embodiment includes, sequentially from an object side to an image plane side along an optical axis, a first lens group having a negative refractive power and including at least one doublet lens, the doublet lens including two lenses, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, wherein the first lens group and the second lens group are configured to move along the optical axis to perform zooming and focusing, and the zoom lens system satisfies 3.0<Vdf/Vdr<6.0, where Vdf denotes an Abbe number of a lens arranged at the object side in a doublet lens, and Vdr denotes an Abbe number of a lens arranged at the image plane side in a doublet lens.