Application of image sharpness criteria in infrared speckle interferometry

Current techniques for infrared speckle interferometry treat all exposures with equal weight regardless of instantaneous atmospheric “seeing”. In an effort to improve accuracy in measurements of visibility amplitude and phase, we utilize measurements of image quality to bin individual exposures. We have investigated several criteria including the second-order moment of the image (an estimate of the Fried parameter) and two sharpness functions considered previously in adaptive optics applications. Test results on bright stars indicate that the sharpness parameters are more sensitive to image quality. These tests also delineate the correlation between sharpness and the second-order moment and demonstrate the variations, sometimes periodic, in image quality caused by atmospheric seeing. Initial tests of a binning technique using real astronomical data exhibit improved accuracy and reduced sensitivity to atmospheric fluctuations.