Fully automated digital holographic interferometer for 360 deg contour and displacement measurements

Abstract

A fully automated optomechatronic system based on an out-of-plane sensitivity digital holographic interferometer is proposed to measure both the 360-deg object’s contour and its surface displacements due to sound stimulation. The digital holograms to measure the surface contour are acquired using the two points of illumination method whose optimal height sensitivity for this particular case is Δ z = 2.98 mm . This method renders a phase map that has a tilt produced by the angle change of the object beam relative to the optical axis, a tilt that is removed by subtracting the phase difference from a physical reference plane tangentially located at the back of the object, which contrasts with former methods that locate this plane usually in the middle portion of the object. By using rotation and averaging matrices, the 360-deg object’s contour digital reconstruction was obtained, and with it, the displacements around the object can be accurately placed on its surface. The main contribution of the proposed fully automated system is to get a 360-deg object’s contour and its surface displacements in a hands-free rapid and accurate evaluation.