The number of effective accumulated frames (NEAF) is defined in this paper. It is proved that SNR in the average accumulated image is increased by M times within NEAF. Further
the techniques of adaptable threshold detection are studied based on image accumulation. the rule of minimal errer probabi lity (ROMEP) is defined and the equation of initlal threshold and the detection probability
false alarm probability as well as error probability are deduced under this rule. The post-processing project is also set up so as to decrease still further false alarm.