Reconstructing volume holograms without image field losses

The reconstruction of volume holograms at wavelengths different from that of hologram formation suffers from the degradation of image quality and thus of an incomplete retrieval of the stored information. The major source of information loss is due to image field reduction. It is shown that these image field losses result from the local violation of Bragg's law induced by spherical recording waves. The evaluation of the spatially varying Bragg condition yields a spherical readout wave necessary for a complete image field reconstruction at an arbitrary wavelength. The effects on resolution are examined qualitatively by visual inspection of test targets.