Methods of Direct Image Transmission
Abstract (Summary)Two interesting new methods for direct image transmission via optical communication channels are presented. In the first of these, the images are transmitted via a serial optical link using phase only encoding and decoding of the image. This is achieved by encoding the image using a set of binary phase sequences and sending the sum of the field from all the pixels through the link. The image is reconstructed by first spatially separating the beam into output pixels and impressing phase sequences conjugate to those used to encode the image onto each pixel. Then the output pixels are combined with a coherent reference beam and the resulting intensities are averaged over the length of the sequences to recover the image. This method is discussed theoretically and it is shown that the number of image pixels able to be transmitted is limited by the dynamic range of the system. An experiment performed to demonstrate the principle of this technique is presented. This is done by transmitting a sixteen pixel image using a liquid crystal spatial light modulator to impart the phase sequences. Reasonably good image transmission is observed. In the second image transmission technique the image is sent directly through a multimode optical waveguide. In this method the amplitudes of the waveguide modes are matched to those of the image pixels by sampling the image correctly and performing an appropriate transform. At the output, the waveguide modes are spatially separated into discrete pixels with amplitudes proportional to those of the original image pixels. This is done by performing another transform and sampling appropriately. Image transmission through a perfectly reflecting slab waveguide and a dielectric slab waveguide is discussed theoretically. Experiments which demonstrate image transmission using this technique and highlight the difficulties encountered are also presented.
Advisor:Prof Tom Barnes
School Location:New Zealand
Source Type:Master's Thesis
Date of Publication:01/01/2001