Modulation light efficiency of diffractive lenses displayed onto a restricted phase-mostly modulation display

I.MORENO; CLAUDIO IEMMI; A.MÁRQUEZ; J.CAMPOS; M.YZUEL

APPLIED OPTICS

Optical Society of America

Año: 2004 vol. 43 p. 6278 - 6284

0003-6935

  In this work we present an analysis of the diffraction efficiency of diffractive lenses displayed onto spatial light modulators depending on the modulation response of the display. An ideal display would produce a continuous phase-only modulation reaching a maximum phase modulation depth of 2p. We introduce the concept of modulation diffraction efficiency, which only accounts for the effect of nonlinearities in the phase modulation of the display. We review a diffractive model to evaluate this modulation efficiency, including modulation defects like nonlinear phase modulation, coupled amplitude modulation, phase quantization or a limited modulation depth. We apply this diffractive model to the particular case of Fresnel lenses and show that these modulation defects produce a lens multiplex effect. Finally we demonstrate that the application of a minimum Euclidean projection principle leads to a very high modulation diffraction efficiency even if the phase modulation depth is far to reach 2p. We demonstrate that the modulation efficiency is greater than 90% for a modulation depth of 1.4p, and greater than 40% (the equivalent for a binary phase element) for a modulation depth of only 0.7p. Experimental results using a twisted nematic liquid crystal display are presented to confirm this situation.