BIAS COMPENSATION IN THE AUTOCORRELATION ESTIMATE FROM INTEREVENT INTERVAL STATISTICS IN CLIPPED DETECTION

The speckle interferometry technique is based on the measurement of th e autocorrelation function. The measurement of intervals between photo events has been proved to be a faster alternative to the direct evalua tion of the correlation function and, under certain conditions, it can provide a better signal-to-noise ratio. However, the validity of this method decreases when the delay value increases since a third-order b ias is present in the autocorrelation estimate. Moreover, when detecti on is clipped as a result of the actual detector characteristics, anot her third-order bias appears. We introduce a procedure to compensate t his bias produced in the autocorrelation estimate when the interval pr obability distribution technique is applied to. The compensated autoco rrelation estimate is obtained by use of a combination of the interval probability distribution and the double-interval probability distribu tion for a series of interval values. By means of this bias compensati on it is possible to evaluate the autocorrelation function correctly f or a wider range of delay values and for higher intensities. (C) 1995 Optical Society of America.