Patent ID: 7320521

Claim:
An optical engine for projecting images comprising: a first PBS cube having a first beamsplitting hypotenuse that reflects first polarization state light beams and transmits second polarization state light beams, said first PBS cube having a first face for receiving first polarization state, first color spectrum light beams transmitted along a first optical axis; a first imaging device placed at a second face of said first PBS cube, for receiving first color spectrum, first polarization state light beams reflected by said first beamsplitting hypotenuse and reflecting first color spectrum, second polarization state light beams having pixel information provided by said first imaging device along a second optical axis towards a fourth face of said first PBS cube, said fourth face of said first PBS cube opposite said second face of said first PBS cube, said first optical axis and said second optical axis being perpendicular to each other; a first quarter-wave plate residing in a plane perpendicular to said second optical axis, said first quarter-wave plate providing half of the phase retardance required for a complete switch of polarization state for polarized light beams passing therethrough along said second optical axis, said first quarter wave plate also providing another half phase retardance resulting in a complete switch of polarization state for polarized beams returning therethrough upon reflection from a dichroic mirror; said dichroic mirror residing in a plane perpendicular to said second optical axis and having a first face and a second face, said first face of said dichroic mirror facing said first quarter-wave plate, said dichroic mirror reflecting light having said first color spectrum and transmits light having a second color spectrum; a second quarter-wave plate residing in a plane perpendicular to said second optical axis that removes half the phase retardance required for a complete switch of polarization state for polarized light beams passing therethrough along said second optical axis, said dichroic mirror residing in between said second quarter-wave plate and said first quarter-wave plate; and a film polarizer disposed at a third face of said first PBS cube and perpendicular to said first optical axis, said film polarizer transmitting light beams having said first polarization state and absorbing light beams having said second polarization state.