Patent attributes
A volume-phase reflection hologram optical element is fabricated by exposing a hologram photosensitive material to two coherent light beams. One exposure light beam has an axis-asymmetric wavefront, and the other exposure light beam has focus points different in the optical axis direction (Z-direction) between on a plane (ZX-plane) including one of two directions (X- and Y-directions) mutually perpendicular on a sectional plane perpendicular to that light beam and on a plane (YZ-plane) including the other of those two directions. Thus, an image display apparatus is realized in which at the time of reproduction, the component of a predetermined wavelength of the image light diffraction-reflected by the hologram optical element is focused at positions different in the optical axis direction between on the ZX-plane and on the YZ-plane, offering different image viewing characteristics between in the X- and Y-directions.
