Television Transmission of Holograms with Reduced Resolution Requirements on the Camera Tube

This paper proposes a technique for the television transmission of a hologram of a two-dimensional transparency. The spatial resolution required on the camera tube is reduced by a factor of four compared with the transmission of a conventional off-axis reference beam hologram. The resolution required is therefore no higher than that required for the direct transmission of the transparency itself. Implementation of the proposed arrangement should be easy. Three holograms formed with an on-axis reference beam are transmitted. The phase of the reference beam assumes the values 0°, 120°, and 240° for the first, second, and third hologram, respectively. The carrier-frequency hologram is "synthesized" from these three on-axis holograms at the receiver. The technique has the further advantage that the undesirable zero-order terms are eliminated. Holograms of two-dimensional transparencies have been transmitted via television.1 The hologram is first formed on the face of the camera tube with an off-axis reference beam and is then transmitted. The main difficulty with this scheme is the high spatial resolution requirement for the camera tube. If the object wavefront has spatial frequencies between -- W and +TF, then the spatial frequencies of the unwanted zero-order terms extend from --2W to 2W. The spatial frequency of the reference beam therefore has to be at least 3W; the highest spatial frequency to be resolved by the camera tube is 4W. (The conditions mentioned, and further discussed in Ref.