A method is proposed for smooth surface roughness measurement. Two standard reference surfaces and two polaroids are employed to realize the measurement. The reversibility of the optical beam is overcome by using two quarter-wave plates. Measuring optical set-up is shown. The mathematical expression of the working principle of the method is derived. The uncertainty of the method is theoretically calculated and digitally simulated. Finally, the feasibility of this method is verified by measuring a standard roughness sample. The measurement result is in accordance with the standard value of the sample roughness provided by the manufacturer.
A novel method based on interferometry for measurement of fine surface roughness is proposed, designed and
completed. The polarization state of the optical beam in one path is changed utilizing a half wave-plate in this design,
avoiding the reversibility of the beam in similar systems previously reported, so that the stability of the system is
ensured. A quarter-wave plate is used to make the consistency of the polarization states of the coherent light to obtain the
better visibility. The absolute measurement values of the surface roughness are achieved using two concentrical beams
scanning the surface. The set-up is simple and easy to be realized. Experiment results show that roughness of
Ra=0.012&mgr;m is achieved.