The DELTA20 T offers 2 illumination modes – Polarized and Non-Polarized. When the instrument is initially turned on it will always be in Polarized mode. To change to Non-Polarized, simply press the black button on either side of the instrument “neck”. To return to Polarized mode, press the button again. If at any time you are unsure what mode you are in, simply turn the instrument OFF and then back ON and it will default to the Polarized mode.