Compact side-viewing interference microscope for inner surface micro-scale topography measurement

Abstract Inner surface micro-scale topography is a concerned aspect in precise pipe-type workpiece manufacturing. To realize nondestructive measurement of pipe-type workpieces, in this paper a compact side-viewing interference microscope (CSIM) is proposed and a prototype is developed. Based on the Michelson-type configuration, a special interference objective is designed, in which the object plane is placed at the side of the objective to realize side viewing. To avoid mechanical scanning and reduce the measuring head size, a polarization interferometric method is employed by using a pixelated polarization camera to achieve phase shifting. The response of four polarization channels is calibrated with a simple spatial carrier method, and the surface reconstruction error is reduced by half with least-squares fittings compensation. Experiments verify that the CSIM achieves high axial resolution and roughness measurement accuracy up to the sub-nanometer level. Two pipe-type workpieces made of different materials, of which the minimum diameter is 42 mm, are successfully measured with the developed CSIM.