the effect of the 3m uniformity tape on the injection of led light from a nominally lambertian led is shown in figure 2a-c. the left image in figure 2a shows the injection cone angle of the led into a light guide under normal tir conditions (+/-42 degrees in a conventional pmma light guide with an optically flat entrance face). the right image shows a close-up view of the left image. figures 2b and 2c (and their details on the right) show the effects of two variations of 3m uniformity tape, with refractive index equal to 1.54 and 1.62, respectively.