Alternate methods of side lobe reduction in holograms

Abstract

High side lobes shown in a hologram efficiency curve are suppressed by reducing the effective sensitivity of a holographic recording medium by a plurality of film layers of gelatin such that there is a continuous increase in sensitivity toward the center of the layers. This makes the recording medium more spectrally selective and increases the 'see-through' characteristic. A holographic fringe pattern with a normally uniform modulation recorded in such holographic medium layers will produce a hologram having a modulation in refractive index which is virtually zero at the surfaces and which increases toward the center of the medium. The layers in the recording medium can have varying degrees of photosensitivity. However, when combined, the layers provide an overall sensitivity which can be depicted as a generally sinusoidal curve. The generally smooth transition in sensitivity from one layer to the next is largely achieved by the mixing of layers at their interfaces.