We present an unscented Kalman filter to identify the phase step imparted to a piezoelectric transducer in phase shifting interferometry in the presence of Gaussian noise. The advantage of the proposed algorithm lies in its ability to determine the phase step values between -pi and pi rad without any prior calibration of the piezoelectric device. The algorithm is tested rigorously by using the simulated data in the presence of Gaussian distributed noise. Experimental validations are also performed in a holographic interferometry optical setup to verify the proposed approach. Once the phase step is identified, the interference phase can be estimated by using the least-squares fitting approach. (C) 2009 Optical Society of America