The rapid development of microelectromechanical systems,
thin-film technology and material research in mechanical behaviours
has provided new impetus to handle high-precision and large-amplitude
deformation measurements. Optical methods are very useful in making
non-contact and full field measurements of the deformation of an
object. However, there is a gap between the sensitivity and the
measurement range in the existing coherent and incoherent optical
methods. In this paper, we propose some approaches to employ time
sequence speckle pattern interferometry to measure large deformations
of pure Ni thin films subjected to bending with high sensitivity. We
introduce a new large deformation measurement system, which includes
a digital speckle interferometry and a micro loading system, and we
propose two methods of phase demodulation in this paper. The new
system is capable of automatically applying micro loading and
continuously capturing the temporal speckle patterns imaged from the
flexural surfaces of the thin film. Forty thousand frames of the
time sequence speckle patterns have been recorded and the maximum
deflection of about 1400 µm has been measured with sensitivities
of λ/2 and λ/4 by the different proposed methods,
respectively.