ISO 17901-1:2015 specifies the terms related to optical characteristics of holograms, the method to measure their diffraction efficiency, and the angular and wavelength selectivity measurement methods. These measurement methods are applicable to any type of hologram if the hologram yields a simple diffraction pattern, which means the reconstructed wave can be clearly separated from other diffracted and non-diffracted waves. In other words, holograms that yield complex diffraction patterns are excluded. There are no restrictions on the materials used to form the holograms.