Backlights are one category of transillumination (in addition to edge and wedge lighting) used to provide light to nonemissive displays. Display technologies where pixels serve only as light valves need some form of light by which the viewer can discriminate the image. This applies primarily to LCD technology. However, some LCD applications, such as military radios, are transflective and depend on ambient illumination for day use. But even in cases such as this, night-time use requires supplemental lighting that is built into the display backplane.
Online access to SPIE eBooks is limited to subscribing institutions.