Characteristics of reflection-type HOEs measured visually

The main parameters of defining the characteristics of a reflection-type holographic optical element, such as diffraction efficiency, the wavelength of the maximum reflection, spectral and angular selectivity, and grating vector directions are measured with a wide angle diverging beam incident normal to the element. Dark ring patterns in the intensity distribution of the beam transmitted through the element allow visual determination of the parameter values. The features of the rings, such as size, shape, thickness, intensity distribution and direction of deviation relative to the center of the distribution are analyzed to determine the parameter values. The results are closely matched with those predicted theoretically.