Cell gap thickness is one of the most important design parameters for liquid crystal displays LCD. Existing measurement methods only apply to transmittive LC cells. These methods are obviously unsuitable for measuring the cell gaps of reflective LCDs with internal reflectors. This kind of LCD includes single polarizer reflective displays and liquid crystal on silicon displays. The objective of this article is to introduce various reflective methods of LCD cell characterization that are both applicable to transmittive and reflective LCDs. © 2002 American Institute of Physics.