In situ 3D profilometry of rough objects with a lateral shearing interferometry range finder

In this paper we describe an interferometric profilometer which provides absolute distance measurements of rough surfaces in the submicrometric range, suitable for in situ application. The apparatus is based on lateral shearing interferometry and works as a range finder. Its main advantages are high acquisition speed, single-shot profile measurements even for moving objects, large field of view and depth of field, full common-path collinear setup, and in situ applicability for automatic measurements. Along with the theoretical study we provide a reconstruction method which makes use of the slope information contained in the fringe pattern to increase resolution, and experimental results that verify the applicability of the system. Our prototype obtains profiles with an aperture of 19 mm from a working distance larger than 90 mm, a depth of field over 4 mm, lateral resolution of 10μm, and depth resolution well below 1μm, at a speed of 30 profiles per second. However, the system can be easily scaled to meet specific application requirements.

► Sensor applicable in situ with high precision and high dynamic range.
► Single shot profile absolute measurements at high speed.
► Use of derivative information to improve resolution of smooth surfaces.
► Accuracy of 40 nm, precision better than σ=88nm from a distance of 90 mm.