A holographic optical element (HOE) is an optical element (such as a lens, filter, beam splitter, or diffraction grating) that is produced using holographic imaging processes or principles. Dichromated gelatin and photoresists are among the holographic recording materials used in forming holographic optical elements.
Holographic optical elements are commonly used in optoelectronics applications such as laser diodes for optical disc drive heads. They have been used in atomic force microscopy (AFM) pickup heads, and were used in the HARLIE (Holographic Airborne Rotating Lidar Instrument Experiment) scanning atmospheric backscatter LIDAR system by NASA.
One use of a holographic optical element is in thin-profile combiner lenses for optical head-mounted displays. A reflective volume hologram is used to extract progressively a collimated image that was directed via total internal reflection in an optical waveguide. The spectral and angular Bragg selectivity of the reflective volume hologram makes it particularly well-suited for a combiner using such light sources as RGB LEDs, providing both good see-through quality and good quality of the projected image. This usage has been implemented in smart glasses by Konica Minolta and Sony.