Patent ID: 8899754

Claim:
A method of controlling a projection-type image display apparatus including a light source for emitting a light beam modulated according to a video signal, a projector that projects the light beam emitted from said light source to display an image, and a changer that changes a polarized state of the light beam emitted from said light source to said projector or that changes a polarized state of the light beam projected by said projector by applying a voltage to a polarized state module comprising a material that changes polarization in response to the applied voltage, said method comprising: repeatedly selecting a plurality of predetermined particular polarized states according to a predetermined sequence; and switching the polarized state changed by said changer to the selected particular polarized states, wherein: the light beam incident on the projector during a first frame period has a first polarization state at the surface at which the beam intercepts the projector; and the light beam incident on the projector during a second frame period which follows the first frame period has a second polarization state, different from the first polarization state, at the surface at which the beam intercepts the projector.