Visual method of measuring reflection-type characteristics of holographic optical elements

A highly diverging laser beam is used to measure angular and spectral selectivities and grating vector direction for reflection-type holographic optical elements (HOE's). The intensity distribution of the beam transmitted from the HOE's reveals dark, ring-shaped patterns. Since these ring patterns are formed as a result of the beam diffracted by the HOE's, the thicknesses and the diameters of the ring patterns convey information on both the angular and the spectral selectivities of the HOE's. In addition the deviation of the ring centers relative to the center of the intensity distribution reveals the grating vector direction. Determination of values related to the ring patterns permits highly accurate measurement of HOE characteristics, such as the upper limit of the diffraction wavelength, the angular and the spectral selectivities, and the grating vector direction. This is proved experimentally.