<title>Development of an optical interferometer for micro-components inspection</title>

Abstract

The application of an optical interferometric system using a Mirau objective to the measurement of the surface profile of micro-components is described. The proposed system produces a uniform monochromatic illumination over the test area and introduces an interference fringe pattern localized near the test surface. Both the interference fringes and the 2D images of the test surface can be focused by an infinity microscope system consisting of a Mirau objective and a tube lens. A piezoelectric transducer (PZT) attached to the Mirau objective can move precisely along the optical axis of the objective. This enables the implementation of phase-shifting interferometry without changing the focus of a CCD sensor as the combination of the Mirau objective and the tube lens provides a depth of focus which is deep in comparison to the phase-shifting step. Experimental results from surface profilometry of the protrutsion/undercut of a polished fiber within an optical connector and of the curved surface of a micro-mirror demonstrate that features in the order of nanometers are measurable. Measurements on standard blocks also show that the accuracy of the proposed system is comparable to an existing commercial white light interferometer and a stylus profilometer.