In this research, a digital circularly polarized heterodyne ellipsometer (DCPHE) is developed, which has a heterodyne interferometer based on a dual-frequency paired circularly polarized laser beam integrated with a digital storage oscilloscope. DCPHE is an amplitude-sensitive ellipsometer that is applicable to real time and precise measurement of ellipsometric parameters. The systematic errors are likewise derived and analyzed. When the incident angle alpha are set at 60 degrees and 70 degrees in DCPHE. an accuracy of less than 0.7% of the ellipsometric parameter measurement of the SiO(2) thin film deposited on silicon substrate is achieved. (C) 2009 Elsevier B.V. All rights reserved.