sorry it took so long for my reply here quantum, just got back... What I mean is, try to have your light source focused so that it isn't too wide a projection.. In other words, you could possibly get a lenz attached to a circular black cup housing and attach it to the top of your light source... This way the light would be more concentrated on your reflective object only... Lets assume my photon theory is incorrect, and reflected light will change the photosensor's state, then if your quest for laser solutions fail, I believe this would be your next best approach... but who knows..