# Recording a Hologram Transmitted over a Communication Channel on One Sideband
## 2 Experimental Recording of a Rainbow Hologram at the Receiving End of the Communication Channel  
A single-step scheme of recording a rainbow hologram is presented in Figure 2, while its version for recording flat colored images is shown in Figure 3. If several flat images are recorded according to the latter scheme, rotating the photographic plate around the vertical axis between exposures, each image will be reconstructed at its own angle during reconstruction, thus providing the parallax effect. The image of holographed object 2, backlit by beam 1, which is coherent with 6, is transmitted to the photographic plate 5 through the filter 4 of vertical spatial frequencies so that, according to [24], [PERSON]'s rainbow hologram is formed. Its speckle structure is extended along the vertical axis and has a complete set of horizontal spatial frequencies (Figure 4). This hologram contains less information on the object because the vertical parallax is absent from it, and in the white light, it recovers a monochrome image, which is iridescent to the onlooker's eyes moving vertically. Its appearance suggests that this hologram may be synthesized with the help of a set of columns composed of short, differently directed segments. A colored image of the object may be obtained, for example, according to the scheme shown in Figure 3, where a slit source 3 with a random phase mask 2 forms an object wave on hologram 5, with the spatial modulation by mask 4. The latter is chosen from different spectral regions of the flat image to be recorded in accordance with Bragg angle \(\theta_{s}\), so that the reconstruction angle would be identical for any of the recorded waves [25]. Figure 2: A schematic of one-step recording of a rainbow hologram, according to the method proposed by [PERSON]: 1—radiation of the object backlighting, which is coherent with the reference beam 6, object 2, holographic plate 5, lens 3, and the filter of vertical spatial frequencies 4. Not only one, but several flat images taken at different angles may be recorded on a holographic plate (Figure 5). These holograms, when irradiated with a beam analogous to the reference one, but with a wide spectral range, will reconstruct the images perceptible as those having a horizontal parallax; they may be considered one of the possible versions of colored 3D displays. It is known that the development of a number of complicated optical-mechanical schemes implementing these colored displays on the basis of [PERSON]'s rainbow holograms have been carried out over some time [26]. However, as a rule, a record of this kind would possess low angle selectivity for thin holograms and low diffraction efficiency because of the rapid exhaustion of the dynamic range of photoresponse. These disadvantages may be eliminated using the DotMatrix technology, in which a photographic plate is divided into a series of so-called holopixels, so that each of them is, in turn, composed of a set of \(j\) regions corresponding to the number of recorded incidence angles. A flat image  
Figure 4: Structure of vertically extended speckles of [PERSON]. [PERSON]’s rainbow holograms with interference fringes oriented transversely at different angles, formed by the interference of spatially filtered object and reference beams (Figure 2). Figure 3: Schematic of recording rainbow focused image holograms. Collimated beam **1** through a random phase mask **2** and a horizontal slit **3** forms, along with transparent **4**, the object beam onto hologram **5**. of the 3D image at only one incidence angle is recorded on each \(j\) region in all holopixels. Irradiation of the obtained rainbow focused image holograms produces a stereo effect, providing a horizontal parallax of a series of approach angles of the colored images of the initial 3D object.