Microbolometer

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A microbolometer is a specific type of bolometer used as a detector in a thermal camera. It is a grid of vanadium oxide or amorphous silicon heat sensors atop a corresponding grid of silicon. Infrared radiation from a specific range of wavelengths strikes the vanadium oxide and changes its electrical resistance. This resistance change is measured and processed into temperatures which can be represented graphically. The microbolometer grid is commonly found in two sizes, a 320×240 array or less expensive 160×120 array. Both arrays provide the same resolution with the larger array providing a wider field of view. Larger, 640×480 arrays were announced in 2005.

1 Advantages
2 Performance limits
3 Origins
4 Companies that currently have licenses to manufacture microbolometer arrays

[edit] Advantages

A microbolometer is an uncooled thermal sensor. Previous high resolution thermal sensors required exotic and expensive cooling methods including Stirling cycle coolers and liquid nitrogen coolers. These methods of cooling made early thermal imagers expensive to operate and unwieldy to move. Also, older thermal imagers required a cool down time in excess of 10 minutes before being usable.

[edit] Performance limits

The sensitivity is partly limited by the thermal conductance of the pixel. The speed of response is limited by the thermal heat capacity divided by the thermal conductance. Reducing the heat capacity increases the speed but also increases statistical mechanical thermal temperature fluctuations (noise). Increasing the thermal conductance raises the speed, but decreases sensitivity.

[edit] Origins

The microbolometer technology was originally developed by Honeywell in the mid 80's as a classified contract for the US Department of Defense. The US Government declassified the technology in 1992. After declassification Honeywell licensed their technology to several manufacturers.