Transmissive optical element based on reflective volumetric gratings

A near-eye display comprising:

• a display module for providing image light to an eyebox;
• and
• a transmissive optical element in an optical path of the image light for redirecting an infrared light beam while transmitting the image light to the eyebox, the transmissive optical element comprising:
• a first outer surface for receiving the infrared light beam at a first beam angle;
• a second outer surface opposing the first outer surface, for outputting the infrared light beam through at a second beam angle, different from the first beam angle;
• a first volumetric grating between the first and second outer surfaces for redirecting, by reflective diffraction, the infrared light beam propagated through the first outer surface;
• and
• a second volumetric grating between the first and second outer surfaces for transmitting the infrared light beam propagated through the first outer surface, for receiving the infrared light beam redirected by the first volumetric grating and for redirecting, by reflective diffraction, the infrared light beam to propagate through the first volumetric grating, through the second outer surface, and out of the transmissive optical element at the second beam angle.

A method for imaging a viewer's eye in a near-eye display, the method comprising:

• illuminating the viewer's eye with auxiliary light;
• redirecting the auxiliary light reflected from the viewer's eye using a transmissive optical element in an optical path of image light carrying images to be viewed by the viewer's eye, the redirecting comprising:
• redirecting the auxiliary light by reflective diffraction on a first volumetric grating of the transmissive optical element;
• and
• redirecting the auxiliary light redirected by the first volumetric grating by reflective diffraction on a second volumetric grating of the transmissive optical element to propagate through the first volumetric grating and exit the transmissive optical element;
• and
• detecting the auxiliary light redirected by the transmissive optical element to obtain an image of the viewer's eye;
• wherein at least one of the first and second volumetric gratings comprises a polarization volume hologram grating configured to selectively redirect light of a first polarization state while substantially transmitting light of a second, orthogonal polarization state.