Design of monitoring thickness and speed of cylindrical part based on laser self-mixing interference in a single-channel system during external grinding

We design a simultaneous measurement of the thickness and speed to monitor mechanical cylindrical parts during external grinding based on a laser self-mixing interference in a single-channel system. If the wavelength is modulated via the laser-injecting-current to generate a frequency shifting corresponding to the rising- and falling- edge of the triangular modulated function. The Doppler frequency caused by the cylindrical part is split into rising- and falling- edge frequencies by the frequency shifting due to wavelength variations. The expressions of the measurement are derived via the derivative of the phase’s polynomial based on the emission-intensity expressions. The frequency shifting is related to the modulation function and the thickness of the cylindrical part. The rising- and falling- edge frequencies of the laser self-mixing interference obtained from the spectrum are used for calculating the Doppler frequency and the frequency shifting for estimating the thickness and the rotation speed of a cylindrical part during external grinding and the results show a good standard derivation less than 10−3 .