Spatial frequency in speckle metrology.

Speckle metrology, as applied to whole field displacement measurements, has been reviewed from the point of view of the relevant frequency domain. It is shown that spatial frequency defines sensitivity and resolution for both pointwise and whole field analysis. Theory and experimental results indicate several ways in which sensitivity can be increased to values comparable with those obtained with moire interferometry. Grating objective speckle measurements have yielded displacement resolutions of <0.6 mum.