Increasing the confidence in whole-field speckle-based optical metrology
transducers requires a detailed understanding of the error sources of
respective instruments. The analysis of error contributions to the optical phase
output of a Michelson-based speckle shearing interferometer have been modelled.
Specific attention has been paid to the effect of the aperture at the image plane,
with respect to collimated and non-collimated object illumination. This modelling
presents an advance on a previous modelled analytical relationship, which
includes partial displacement derivative terms and components as a function
of illumination geometries and, importantly, aperture effects. The work has
identified a phase error contribution due to the aperture function of between
0.15% and 1.48%, dependent on the object distance, when considering a planar
object undergoing predominantly surface to normal deformation
