Analysis and elimination of boundary reflections in transmission holograms

Elimination of reflections which occur at the glass-air interface of holographic plates is an important factor to be taken into account when recording transmission holograms. If these reflections are not eliminated, unwanted secondary gratings are stored due to interference of the object and reference beams with the beams reflected at the interface. This not only gives rise to an anti-aesthetic effect, but also produces a reduction in diffraction efficiency and an increase in noise. We present the results obtained using a method which eliminates these unwanted reflections. This method, instead of using liquids, makes use of a black self-adhesive PVC masking tape stuck on the glass side of the holographic plate. We carried out a qualitative analysis of the different results obtained for plates with and without black PVC tape and also quantitatively analyzed the effect of the tape on the reflectivity of the plates as well as the density of holographic gratings. The results obtained confirm the applicability of the method described for antihalation reduction and elimination of unwanted reflections that cause interference affecting the quality of the holographic image. (C) 1999 Elsevier Science Ltd. All rights reserved.