application of uniformity tape also appears to provide ancillary benefits. when applied to the input edge of the light guide, the optically clear adhesive will wet out and conform to the surface roughness of the light guide edge so that the film and light guide were optically coupled (i.e., no air is trapped between them). as a result of this optical coupling, the pmma plate does not require the level of polishing required in a conventional light guide; this suggests that uniformity tape could lead to a reduction in manufacturing steps and lower costs.