Patent ID: 6313893
Filing Date: 2001-11-06
Classification: G02F

Abstract:
A system for DC balancing of liquid crystal displays, comprising:an odd number multiple quarter-wave compensator having first and second states, wherein said compensator is adapted to propagate light with a shifted polarization when in said first state and to propagate light with a polarization which is unshifted when in said second state;an odd number multiple quarter-wave imager disposed such that is it in series with said compensator, said imager having first and second states wherein said compensator is adapted to propagate light with a shifted polarization when in said first state and to propagate light with a polarization which is unshifted when in said second state;wherein, in operation, said system is arranged such that in a reflective mode operation, incoming light enters said system and travels through said compensator, then through said imager in a direction which is away from said compensator, then returns to travel through said imager in a direction which is toward said compensator, and then travels through said compensator in a direction which is away from said imager, and wherein as the light travels through said system its polarization is influenced by the operative state of said compensator and said imager such that when said imager and said compensator are both in said first state or both in said second state, light is not output, but when said imager and compensator are in different states with respect to the other said system is arranged to transmit output light to thereby provide optical efficiency for reflective mode operation.