When you need continuous surveillance of city borders or property of a large facility in any environment or condition, a long-range thermal camera system is perfect for the job. There are two types of thermal camera systems available for these applications, cooled and uncooled. We would like to break down the technical differences between the two, and explain the costs and benefits associated with each to help you decided on the right one.
The video above compares the level of detail between cooled and uncooled footage in 640×480 resolution with objects that are far and near.
Cooled Thermal Camera
A cooled thermal camera’s imaging sensor is integrated with a cryocooler. The cryocooler lowers the sensor temperature to cryogenic temperatures. This drop in sensor temperature is necessary to lessen thermally induced noise to a level below that of the signal from the scene being imaged. Cooled thermal cameras are more sensitive to small differences in scene temperature than are uncooled cameras, making cooled cameras more suitable for extremely long-range imaging in low-contrast scenes.
Uncooled Thermal Camera
Uncooled infrared cameras do not use cryogenic cooling. A common detector design is based on the microbolometer, a tiny vanadium oxide resistor with a large temperature coefficient on a silicon element with large surface area, low heat capacity and good thermal isolation.
Cooled or uncooled? What to choose?
With all of the advantages of uncooled cameras in mind, it begs the question: why use cooled cameras? The answer: when standoff ranges reach 5km or greater, cooled thermal cameras systems quickly become more cost-effective. Note the emphasis on the word \”systems\” – the camera is the only component of an imaging \”system\”. One of the biggest cost drivers of a long-range uncooled camera system is the lens. As effective range requirements increase, the lenses for uncooled camera systems become so bulky and expensive that it can often be cheaper to specify a cooled camera with an equivalent focal length lens.
Long-range thermal surveillance applications require long focal length lenses. The cost of lenses increases rapidly with focal length for uncooled camera systems and rather slowly for cooled systems. As a result, even though the cost of a cooled camera core is much higher than an uncooled core, the system cost (core plus lens) for uncooled surpasses cooled system cost at a focal length on the order of 350mm. Useful imaging of man-sized targets at long ranges requires focal lengths that exceed 350mm. Therefore, long-range imaging of man-sized targets is less expensive with a cooled camera system, at least when only considering system acquisition cost.
It is important to take the 8,000-10,000 hour lifetime of cryocoolers into account when trying to arrive at the best solution. If the cryocooler needs a servicing every 2 years, and the cost is 10% of the total system, then the 4-year cost of the cooled system is really 1.2X the initial system cost.
Having more than 20 years of experience with thermal imaging cameras, and supplying both cooled and uncooled systems, ThermalVideo.com can always provide you with the necessary information to make a well-informed decision for your particular application.
Data from FLIR Systems Technical Notes