Temperature-Compensated Imaging Lens Layout for Small Surveillance Cameras
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Solution Overview
Problem
Small-sized surveillance cameras experience significant changes in resolution due to temperature fluctuations, making it challenging to maintain high optical performance under varying temperature conditions.
Innovation Solution
An imaging lens system comprising multiple lenses, including a temperature compensation lens with a refractive index temperature coefficient of 10 (10−6/° C.) or less, and strategically positioned stops to maintain optical performance across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional small-sized surveillance cameras are used, then the device size is reduced, but the optical performance changes significantly with temperature
Solution Approach 1:
The patent applies parameter changes by selecting lens materials with specific refractive index temperature coefficients (DTn). The first lens uses material with DTn of 20 or more, while the second lens uses material with DTn of -80 or less, creating a temperature compensation effect that maintains optical performance across temperature ranges while keeping the camera compact.
Solution Approach 2:
The patent employs composite material strategy by combining lenses made from different materials with contrasting thermal-optical properties. The first lens uses material with high positive DTn (20 or more) while the second lens uses material with large negative DTn (-80 or less), creating a composite optical system that compensates for temperature-induced focal length changes.
2Reliability
If temperature compensation is implemented using lenses with specific refractive index temperature coefficients, then optical performance stability is improved, but the device complexity increases
Solution Approach 1:
The patent manages complexity by focusing parameter changes on two critical lenses (first and second lenses) rather than redesigning the entire optical system. By controlling the DTn parameters of these two lenses specifically, the system achieves temperature compensation without requiring complex redesign of all lens elements.
Solution Approach 2:
The patent applies local quality by assigning specific material properties only to the first and second lenses that are most sensitive to temperature changes. The first lens uses material with DTn ≥ 20 and the second lens uses material with DTn ≤ -80, while other lenses can use conventional materials, thus achieving temperature compensation without uniformly increasing complexity across the entire lens system.
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 ensures consistent optical characteristics and reduced back focal length variation, enhancing imaging quality across extreme temperature ranges from -40°C to 80°C.
Implementation Method 1
One of the first to ninth lenses is a temperature compensation lens having positive refractive power and having an absolute value of a refractive index temperature coefficient of 10 (10−6/° C.) or less
Data Source
AI summary
An imaging lens system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens disposed in order from an object side. One of the first to ninth lenses is a temperature compensation lens having positive refractive power and having an absolute value of a refractive index temperature coefficient of 10 (10−6/° C.) or less.