Variable Magnification Optical System Chromatic Aberration Correction
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Solution Overview
Problem
Surveillance camera optical systems face challenges in achieving high optical performance and correcting chromatic aberrations across a wide wavelength band from visible to near-infrared ranges, especially with the increasing demand for high-resolution imaging devices, while maintaining a small size and large relative aperture.
Innovation Solution
A variable magnification optical system comprising four lens groups with specific refractive powers and configurations, where the first and third lens groups are fixed, and the second and fourth lens groups move to adjust magnification, with cemented lenses and aspherical surfaces to correct chromatic aberrations, satisfying conditional formulas for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the optical system uses a conventional four-lens-group structure with positive-positive-positive-negative arrangement, then the system can achieve variable magnification and compact size, but chromatic aberration correction deteriorates in the near-infrared range
Solution Approach 1:
The patent changes the refractive power parameters of the lens groups, specifically making the second lens group have negative refractive power and the fourth lens group have positive refractive power. This parameter adjustment enables the system to correct chromatic aberrations across a wide wavelength band from visible to near-infrared ranges while maintaining variable magnification capability and compact size.
Solution Approach 2:
The patent employs composite lens structures where the first lens group consists of three lenses with specific refractive powers (positive, positive, negative) and the second lens group consists of four lenses with specific refractive powers (negative, positive, negative, negative). This composite arrangement of different lens types and materials enables simultaneous correction of chromatic aberrations and maintenance of compact size with variable magnification.
2Measurement precision
If the optical system increases resolution performance for high-resolution imaging devices, then image quality improves, but the system size and complexity increase
Solution Approach 1:
The patent divides the optical system into four distinct lens groups with specific functions: the first lens group (positive, positive, negative) handles chromatic aberration correction, the second lens group (negative, positive, negative, negative) manages magnification change, the third lens group (positive, negative) assists in focusing, and the fourth lens group (positive) corrects image plane. This segmentation allows each group to be optimized for its specific function, achieving high resolution without increasing overall system size.
Solution Approach 2:
The patent applies local quality by giving different regions of the optical system different characteristics. The first lens group has specific refractive power combinations for chromatic aberration correction, while the second lens group has negative refractive power for compact magnification change. This localized optimization of lens properties enables high resolution performance without requiring a larger overall system.
3Illumination intensity
If the optical system maintains a large relative aperture for low illumination photography, then image quality in low light improves, but chromatic aberration correction becomes more difficult
Solution Approach 1:
The patent adjusts the refractive power parameters of the lens groups to maintain a large relative aperture while correcting chromatic aberrations. Specifically, the first lens group has positive refractive power for aperture maintenance, the second lens group has negative refractive power for compact design, and the fourth lens group has positive refractive power for chromatic aberration correction in the near-infrared range.
Solution Approach 2:
The patent uses a composite lens structure with the first lens group consisting of three lenses (positive, positive, negative) and the second lens group consisting of four lenses (negative, positive, negative, negative). This composite arrangement enables the system to maintain a large relative aperture for low illumination photography while simultaneously correcting chromatic aberrations across the visible to near-infrared spectrum.
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 achieves excellent chromatic aberration correction and high optical performance across a wide wavelength band, supporting high-resolution imaging devices while maintaining a compact size and large aperture, enabling high-quality imaging in both day and night conditions.
Implementation Method 1
an optical system that can satisfy these two demands is requested... chromatic aberrations need to be excellently corrected in a wide wavelength band from a visible range through a near-infrared range
Implementation Method 2
cemented lenses and aspherical surfaces to correct chromatic aberrations... excellent chromatic aberration correction... across a wide wavelength band
Data Source
AI summary
A variable magnification optical system consists of a positive first lens-group, a negative second lens-group, a positive third lens-group and a positive fourth lens-group in this order from an object side. The first lens-group and the third lens-group are fixed when magnification is changed from a wide-angle end to a telephoto end, and the magnification is changed from the wide-angle end to the telephoto end by moving the second lens-group toward an image side, and correction of an image plane and focusing, which have been necessitated by magnification change, are performed by moving the fourth lens-group. The first lens-group consists of two positive lenses and a negative lens in this order from the object side. The second lens-group consists of a negative 21st lens, a positive 22nd lens, a negative 23rd lens and a negative 24th lens in this order from the object side.