An optical system for a head-worn computer may include a light source positioned within the head-worn computer and adapted to project non-polarized illuminating light towards a partially reflective partially transmissive surface such that the illuminating light reflects through a field lens and towards a reflective display and a polarizing film adjacent to a surface of the reflective display that polarizes the illuminating light after it passes through the field lens. The illuminating light reflects off a surface of the reflective display, forming image light which is then analyzed by the polarizing film prior to being transmitted through the field lens and then through the partially reflective partially transmissive surface to a non-polarizing lower display optical system adapted to present the image light to an eye of a user wearing the head-worn computer.