Addition fringe patterns are obtained in real time with electronic spe
ckle pattern interferometry (ESPI) when two pulses are fired within a
single field of a CCD camera, i.e., within 1/50 s. The ability to use
ESPI in this manner means that target deformation can be studied in ve
ry severe environments. A major drawback is that the addition fringes
are intrinsically noisy and of very low contrast, impeding a full anal
ysis of the deformation. Experimental results are presented for two me
thods of reducing noise in addition fringe patterns: subtraction of a
reference frame and subtraction of addition fringe patterns. The subtr
action procedure leads to high-contrast fringes, which can contain inf
ormation of both target deformation and rigid body motion. An analytic
al representation of this behavior is presented.