February 26,2024By:Innova OpticsView:218
Long-distance monitoring in low light or complete darkness is a perfect application for thermal imaging technology. This type of monitoring is often used in border areas or wide areas where most threats occur at night. Thermal imaging cameras launched on the market for medium and long-distance monitoring provide users with a variety of choices. Users often ask: Should I use a cooled or uncooled thermal imaging system? Which system is the most cost-effective?
The security industry market is very price sensitive and extremely competitive. When purchasing any expensive thermal imaging system for mid- to long-range surveillance, a case-by-case analysis is required. This is especially true when there are other systems on the market that offer comparable functionality and cost less. This technical note describes the two types of long-range thermal imaging camera systems available on the market today: cooled and uncooled systems. There is a considerable difference in component costs between the two systems, so it is extremely important in deciding which system to choose.
Cooled Thermal Imager
Modern cooled thermal imagers have a cryogenic cooler integrated into the imaging sensor. This device can cool down the sensor. Lowering the detector temperature is to make the thermal noise signal lower than the imaging signal.
The moving parts of cryocoolers have extremely tight mechanical tolerances and wear out over time, and helium can slowly leak out. After 8,000-10,000 hours of use, the cryocooler must be replaced.
Cooled thermal imaging cameras are the most sensitive to small temperature differences in the scene. They can detect the tiniest temperature differences between objects. This thermal imaging camera can image in the mid-wave infrared, or mid-wave infrared band of the spectrum, and the thermal contrast in this band is highly dependent on blackbody physics. Thermal contrast is the change in signal caused by changes in target temperature. The higher the thermal contrast, the easier it is to detect targets that are not too different in temperature from the background.
Generally speaking, the contrast of mid-wave infrared thermal imaging cameras at night is sharper than that of infrared thermal imaging cameras in other bands. Cooled thermal imagers can also be designed to operate in the long-wave infrared or LWIR band.
Uncooled Thermal Imager
The imaging sensor of an uncooled thermal imager does not require cryogenic refrigeration. The detector it uses is usually based on a microbolometer. This detector is composed of a small vanadium oxide resistor with a very large temperature coefficient and a silicon element. It has the characteristics of large area, low heat energy and good thermal insulation performance. . Changes in scene temperature cause changes in bolometer temperature, and these changes are converted into electronic signals that are then processed into images. Uncooled sensors are designed to operate in the long-wave infrared, or LWIR, band with wavelengths from 7 to 14 microns. In this environment, land temperature targets emit most of their infrared energy.
Uncooled thermal imaging cameras are generally cheaper than cooled infrared thermal imaging cameras, and their sensors are less expensive to manufacture.There are fewer steps than refrigeration sensors, the output is higher, and the vacuum packaging cost is also cheaper. In addition, uncooled thermal imaging cameras do not require expensive equipment such as cryogenic refrigerators.
Uncooled thermal imaging cameras have fewer moving components and last longer than cooled thermal imaging cameras under the same operating conditions. In security applications, thermal imaging cameras are often required to work continuously to avoid missing any threats. Cooled thermal imaging cameras generally require maintenance after 1 to 2 years of use, while non-cooling thermal imaging cameras can continue to operate for many years.
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