Abstract: An automatic adjustable radiant energy filter system adapted for protecting uman eyes (and other optical devices) from dangerous intensities of laser light or other types of radiation during experimentation therewith is disclosed as including a pair of relatively moving polarized filters, one of which is automatically positioned with respect to the other as a consequence of a unique photodetector and negative feedback system combination sensing and controlling the aforesaid laser light radiation that passes therethrough in accordance with a predetermined intensity level.