Variable Magnification Optical System for Wide Wavelength Surveillance
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Solution Overview
Problem
Surveillance cameras require an optical system that maintains high optical performance across a wide wavelength band from visible light to near-infrared ranges, especially with increasing pixel counts and varying illumination conditions, while being compact and cost-effective.
Innovation Solution
A variable magnification optical system comprising a first lens group with negative refractive power and a second lens group with positive refractive power, where the first lens group includes a negative meniscus lens and a cemented lens, and the second lens group includes a positive lens with an aspheric surface, allowing for magnification changes by adjusting the distance between the groups and correcting image plane positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical system is designed for high optical performance across wide wavelength band (visible to near-infrared), then chromatic aberration correction is improved, but device complexity increases
Solution Approach 1:
The optical system is divided into multiple lens groups with specific functions: a first lens group for chromatic aberration correction across wide wavelength bands, a second lens group for magnification adjustment, and a third lens group for focus control. This segmentation allows each group to be optimized for its specific function, achieving high optical performance while managing overall system complexity.
Solution Approach 2:
The patent employs composite lens structures including cemented lenses combining materials with different dispersion properties (e.g., high dispersion and low dispersion glass). This allows effective chromatic aberration correction across the visible to near-infrared wavelength range by compensating for wavelength-dependent refraction differences through material composition rather than increasing overall system complexity.
2Measurement precision
If pixel count is increased to improve image quality, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The optical system performs preliminary correction of chromatic and spherical aberrations before light reaches the image sensor through carefully designed lens groups. This preliminary action ensures that even with high pixel counts, the incoming light is already optimized, allowing the sensor to capture high-quality images without requiring additional complex processing or correction mechanisms.
3Adaptability or versatility
If lens groups are moved to change magnification, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent implements a dynamic zoom mechanism where the second lens group (having positive refractive power) is movable relative to the first and third lens groups. By moving this intermediate lens group along the optical axis, the magnification is continuously adjustable while maintaining focus through coordinated movement with the third lens group. This dynamic design provides versatility in magnification adjustment while using a relatively simple mechanism compared to moving all lens elements.
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 provides high optical performance and image quality across the visible and near-infrared ranges, effectively addressing the need for improved surveillance camera optics in both day and night conditions with increased pixel density.
Implementation Method 1
a positive lens with an aspheric surface, allowing for magnification changes by adjusting the distance between the groups and correcting image plane positions
Implementation Method 2
the first lens group includes a negative meniscus lens and a cemented lens, and the second lens group includes only two cemented lenses
Data Source
AI summary
A variable magnification optical system consists of a first lens-group having negative refractive-power, a stop and a second lens-group having positive refractive-power in this order from an object-side. The first lens-group includes an L11 negative meniscus lens, an L12 negative lens and a C11 cemented lens, in which a biconcave lens and a positive lens are cemented together in this order from the object-side, in this order from the object-side. The second lens-group includes an L21 positive lens that is arranged closest to the object-side and includes at least one aspheric surface, and an object-side surface of which is convex, and only two cemented lenses toward an image-side of the L21 positive lens, and each of which consists of a negative lens and a positive lens cemented together in this order from the object-side. The following conditional expressions (1) and (2) are satisfied:−1.0<Rf11/Rf12<0.7 (1); and55.0<νdave1 (2).