Effect of Speckle Size in Edge Point Referencing for Deformation Measurement

When an object is subjected to mechanical or thermal loading, the surface of object deforms. Deformation of the object can be measured using holography techniques. However, the holography technique is restricted due to the requirement of a vibration isolation system to keep the reference beam stable. Without the reference beam, we can only obtain the autocorrelation from an intensity recorded in the Fourier plane. In a previous study, we proposed that object information can be retrieved by utilizing a phase retrieval iterative algorithm or by recording two shots by modifying the field near the edge of the object by incorporating edge point referencing. We also demonstrated that deformation can be sensed in a single shot by increasing the intensity of the additional beam. In this paper, we explore how the quality of the deformation measurement is affected if the beam illuminating the edge of the object is not tightly focused.