This work shows a characterization and a polarimetric analysis of a Liquid Crystal on Silicon (LCoS) display, device that works with reflection of the light. We have observed that the optical axis of the LCoS display molecules fluctuates as a function of the time as a consequence of the type of electrical signal addressed to the device. These time fluctuations lead to two different physical phenomena that may decrease the efficiency when addressing diffractive elements to the display: the effective depolarization and the phase-fluctuations phenomena. We have developed a study of these two phenomena and its influence on diffractive elements. In particular, two different characterization methodologies suitable to obtain the Mueller matrix of the LCoS display are shown. The obtained results are provided and processed to perform a polarimetric study. Next, an intensity or a phase optimization of the LCoS display response is done, in order to obtain configurations of external polarizers and waveplates that allow us to improve the use of this device in optical applications. This study is done as a function of the incident angle and as a function of the wavelength, in order to detect the influence of these parameters on the effective depolarization origin and of the phase-fluctuations. In addition, we have analyzed the influence of the phase-fluctuations phenomena on the efficiency of a phase grating and a digital hologram addressed to the LCoS display.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.