Introduction To Microbolometers - Teledyne FLIR A68 Series User Manual

Introduction to Microbolometers

A microbolometer is an uncooled thermal sensor used as a detector in an infrared
camera. FLIR A68/A38 series cameras are sensitive to thermal energy at long wave
infrared (LWIR) wavelengths ranging from 8 μm to 14 μm (infrared wavelengths span
from 710 nm – 1 millimeter). The FLIR A68/A38 series uses IR filtering lens that only
allow these specific wavelengths to pass to the detector.
All objects emit electromagnetic radiation and the amount of radiation emitted at each
wavelength depends on the temperature of the object. Hot objects emit at short
wavelengths and cold objects emit more at long wavelengths.
Infrared radiation strikes the detector material, heating it, and thus changing its
electrical resistance. This resistance change is measured and an analog-to-digital
converts the signal into a 16-bit value which is used to create an image. Unlike a
traditional image sensor, there is no exposure time to fill a pixel well with photons; the
microbolometer sensor is constantly exposed to incoming radiation and the readout
circuit samples the pixel values to create the frame. When in free-running mode, the
FLIR A68/A38 series reads frames at 30fps (this rate can be lowered by skipping
frames or using one of the frame trigger modes).
FLIR A68/A38 Series IR Camera User's Manual Introduction to Microbolometers • 23