COHERENT VERSUS INCOHERENT LADAR DETECTION AT 2.09-MU-M

A 2.09-mu m ladar system is built to compare coherent to incoherent de tection. The 2.09-mu m wavelength is of interest because of its high a tmospheric transmission and because it is eyesafe. The 2.09-mu m syste m presented is capable of either a coherent or incoherent operational mode, is tunable in a small region around 2.09 mu m, and is being used to look at the statistical nature of the ladar return pulses for typi cal glint and speckle targets. To compare coherent to incoherent detec tion the probability of detection is investigated as the primary perfo rmance criterion of interest. The probability of detection is dependen t on both the probability of false alarm and the probability density f unction, representing the signal current output from the detector. The se probability distributions are different for each detection techniqu e and for each type of target. Furthermore, the probability of detecti on and the probability of false alarm are both functions of the domina ting noise source(s) in the system. A description of the theoretical e xpectations of this system along with the setup of the ladar system an d how it is being used to collect data for both coherent and incoheren t detection is presented.