Analysis of 320X240 uncooled microbolometer focal plane array ...

172.2.3 NoiseThe detection capability of any imaging system is limited by fluctuations of a randomnature, noise. There are three categories that the noise appearing in an infrared systemmay arise from: noise in detectors, in readout electronics, and from the radiationbackground. In a microbolometer UFPA, there are three primary noise sources to beconsidered. The Johnson noise of the bolometer, the 1/f noise characteristic of bothamorphous and poly-crystalline semiconductors, and the fundamental thermodynamictemperature fluctuation noise of the individual detector elements. Also, there are noisefrom the readout electronics and the detector bias supply, but the common-mode noiserejection features that are incorporated into Rockwell's design of UFPA effectivelysuppresses the noises.The Johnson noise or thermal noise appears in any resistive material. It is causedby the random motions of the charge carriers. 1/f noise or current noise is a dominantnoise source of semiconductor materials at low frequencies. The background noise is dueto the quasi-random arrival of photons from the surrounding of the detector. Thebackground noise ultimately limits the performance of any thermal detector, because thenoise from the background still exists even if all of the other noise is suppressed. Due tostatistical nature of the heat interchange with the surrounding, a thermal detector incontact with its environment by conduction and radiation exhibits random fluctuations inits temperature, known as temperature fluctuation noise. The temperature fluctuationnoise not only comes from the source background, but also from detector casing,electronics, and even the detector itself.