Spectroscopic Ellipsometry provides information about optical and structural properties of material and thin film by observing the change in the state of polarization (amplitude and phase) when a beam of polarized light reflects from the surface of a sample. The UT-300 uses a spectroscopic ellipsometer containing a PEM element as the principle for phase modulation measurement. By directing the linearly polarized beam through the PEM, as shown below, the light is converted into an elliptically polarized light which is phase-modulated at a 50 kHz frequency. For this reason, the system can determine and with a resolution of mere milliseconds. The short measuring time of 1ms is obtained both because of the characteristics of PEM and its high frequency. The unit produces a very accurate measurement, as it can detect sin in addition to cos. This is why fast and highly accurate measurement is possible without mechanical vibration.