Retarder stack for preconditioning light for a modulator having modulation and isotropic states of polarization

A retarder stack for preconditioning at least partially polarized light for input to a modulator which modulates one polarization more than another, comprising

• a polarizer for receiving input light and outputting the at least partially polarized light;
• a first retarder having a first retardance and a first orientation with respect to said at least partially polarized light, for receiving said as least partially polarized light and outputting initially transformed light;
• and
• a second retarder having a second retardance and a second orientation with respect to said at least partially polarized lights for receiving said initially transformed light and outputting light comprising a first portion of output light having a predetermined first spectrum and a second portion of output light having a predetermined seconded spectrum, wherein said polarizer, said first retarder, and said second retarder are selected such that said first portion of output light has a polarization that would not be modulated by the modulator and said second portion of output light has a polarization that would be modulated by the modulator.

A retarder stack for selectively outputting light for input to a modulator which modulates one polarization more than another, comprising:

• a first retarder having a first retardance and a first orientation with respect to an at least partially polarized light, for receiving said at least partially polarized light and outputting initially transformed light;
• a second retarder having a second retardance and a second orientation with respect to said at least partially polarized light for receiving said initially transformed light and outputting light comprising a first portion of output light having a predetermined first spectrum and a second portion of output light having a predetermined second spectrum, wherein said polarizer, said first retarder and said second retarder, are selected such that a polarization of said first portion of output light and a polarization of said second portion of output light are orthogonal and such that the polarization of said first portion of output light would be modulated by the modulator more than the polarization of said second portion of output light;
• and
• an analyzer for receiving said output light and outputting one of said first portion of output light and said second portion of output light.