Patent ID: 6975456

Claim:
Illumination apparatus for forming an output beam, the apparatus comprising: (a) a light source adapted to emit a source beam of linearly-polarized light in a downstream direction along an optical axis, said source beam having a polarization direction transverse to said axis; and (b) a fixed birefringent plate having first and second regions with different rotational properties such that said first region of said plate intercepts a first portion of said source beam and said second region intercepts a second portion of said source beam, said first and second portions altering the polarization of said first and second portions of said source beam by different amounts so as to form an altered beam having a first portion with a first polarization direction and a second portion with a second polarization direction transverse to said first polarization direction, said first portion having a first intensity distribution relative to said optical axis, said second portion having a second intensity distribution relative to said optical axis; (c) an optical element disposed between said light source and said birefringent plate, said optical element focusing light from said light source at a focal location on said optical axis; and (d) at least one polarization-selective element mounted downstream from said birefringent plate, said at least one polarization-selective element having a transmission axis and being operative to allow transmission of light having a polarization direction parallel to said transmission axis and to prevent transmission of light having a polarization direction perpendicular to said transmission axis.