Holographic displacement measurements in fluid and solid mechanics: immunity to aberrations by optical correlation processing

J. M. Coupland, N. A. Halliwell

Abstract

The measurement of three–dimensional vector displacements in fluid and solid mechanics using holography is severely restricted by aberration which prevents the reconstruction of a high fidelity real image. This paper demonstrates how immunity to aberrations can be achieved through complex (i.e. optical) autocorrelation of the wavefront amplitude distribution emanating from a region of the real image. Theory is presented which shows that, by the use of optical autocorrelation, aberration associated with high numerical aperture (NA) holographic recordings necessary for good ‘depth’ resolution is, within well defined limits, of no consequence. Further to this, a three–dimensional vector displacement is obtained from just one ‘view’ into the real image.