An input device (300) is provided for use with an image projection system (100). The input device (300) includes a first end (309) having a photodetector (302) and a second end (310) having a phototransmitter (303). An image projection system output beam (124) of photons is projected on a projection surface (140) along with a projected image (128). When the photodetector (302) receives the image projection system output beam (124), the phototransmitter (303) delivers a transmitted beam (324) back to the image projection system (100). The input device (300) can be equipped with user control mechanisms so as to act as a mouse or otherwise control the image projection system (100).