| 摘要 |
A diffractive optical element (10) for guiding a light having a color spectrum characterized by a plurality of wavelengths longer than a shortest wavelength, lambda B, and shorter than a longest wavelength lambda R, the light striking the diffractive optical element (10) at an angle greater than a first field-of-view angle, alpha<->FOV, and smaller than a second field-of-view angle, alpha<+>FOV. The diffractive optical element comprising a linear grating (12) being formed in a light-transmissive substrate (14). The linear grating (12) is characterized by a pitch, d, selected so as to allow total internal reflection of a light having wavelength lambdaB and a striking angle of alpha <->FOV. The light-transmissive substrate is characterized by an index of refraction, etaS, larger than a minimal index of refraction, etamin, which is selected so as to allow total internal reflection of a light having wavelength of lambdaR and a striking angle of alpha <+>FOV. |
