Patent ID: 8098439

Claim:
An optical device, comprising: a display source; an imaging optical module; and a projection mechanism, including a light-transmitting substrate, an input aperture and an output aperture defined by non-overlapping surface areas on the substrate and an exit pupil spaced apart from the output aperture, light from the imaging optical module being projected to the exit pupil, the light-transmitting substrate having at least two major parallel surfaces, optical means for coupling light emerging from the display source into the substrate by total internal reflection, and at least first, second and third partially reflecting surfaces located in the substrate for coupling the light out of the substrate, wherein the orientations between the partially reflecting surfaces and the exit pupil define first, second and third incident angles at the partially reflecting surfaces, the partially reflecting surfaces being coated with three different coatings so that at the third incident angle, the reflectance from the third surface is higher than the reflectance from the second surface, at the second and the third incident angles, the reflectance from the second surface is higher than the reflectance from the first surface, and the reflectance from the second partially reflecting surface at the second incident angle, is higher than the reflectance at the third incident angle.