An original configuration of a photo-polarimeter with a blazed diffraction grating as central element is proposed for a newel ellipsometric set up. It produces two measurement beams corresponding to the grating diffraction orders +/- 1. The third beam, corresponding to the diffraction order 0, is back-reflected for the real time alignment of the photo-polarimeter by the autocollimation method. Each of the two diffracted beams passes through a beam splitter to be resulted in the four beams required for the measurement. The light intensity is measured by either four silicon detectors or four small photomultipliers and data are collected by four parallel ADC channels. In order to evaluate the measurement speed of the ellipsometer constructed using these new polarimeters, the change of the polarization state produced by a photo-elastic modulator oscillating at 50 kHz was measured in real time. (C) 2004 Elsevier B.V. All rights reserved.