It is difficult, as we know, to search for interference fringes in Linnik white light interferometry with an extremely short coherence length because of the optical path mismatch of two interference arms and out of focus of the reference mirror and the test surface. An automated method to tackle this problem is presented. The determination of best foci of the reference mirror and the test surface is implemented by the astigmatic method based on a modified commercial DVD pickup head. The astigmatic method is improved by setting a threshold value in the Sum Signal (SS) to truncate the Normalized Focus Error Signal (NFES). The Truncated NFES (TNFES) has a monotonic relationship with the displacement of the test surface and the zero crossing point identifies true focus. The developed autofocus system is confirmed experimentally with a dynamic range of 190 μm, average sensitivity of 70 mV/μm, average standard deviation of 0.041 μm, displayed resolution of 4.4 nm and accuracy of 55 nm. The minimization of Optical Path Difference (OPD) of two interference arms is carried out by finding the maximum fringe contrast of the image captured by a CCD camera with the Root Mean Square Fringe Contrast (RMSFC) function. Experimental tests show that the automated method can be effectively utilized to search for interference fringes in Linnik white light interferometry.