Vibration measurement of miniature component by high-speed image-plane digital holographic microscopy

Abstract

Measuring deformation of vibrating specimens whose dimensions are in the submillimeter range introduces

a number of difficulties using laser interferometry. Normal interferometry is not suitable because

of a phase ambiguity problem. In addition, the noise effect is much more serious in the measurement of

small objects because a high-magnification lens is used. We present a method for full-field measurement

of displacement, velocity, and acceleration of a vibrating miniature object based on image-plane digital

holographic microscopy. A miniature cantilever beam is excited by a piezoelectric transducer stage with a

sinusoidal configuration. A sequence of digital holograms is captured using a high-speed digital holographic

microscope. Windowed Fourier analysis is applied in the spatial and spatiotemporal domains

to extract the displacement, velocity and acceleration. The result shows that a combination of imageplane

digital holographic microscopy and windowed Fourier analyses can be used to study vibration without

encountering a phase ambiguity problem, and one can obtain instantaneous kinematic parameters on

each point.