ABSTRACT
The primary application of Fourier optics in image processing is the optical correlator system. The system design involves the calculations of both ray optics and diffraction integrals. This is the subject of Section 6.2. In order to construct a correlator system, an essential element was the complex spatial filter. Vander Lugt developed a technique for recording a complex spatial filter in 1966 and constructed the first correlator based on this in the same year [264]. The spatial filter in this correlator was recorded on a holographic recording material, which had to be processed and replaced in the system after processing. Holographic recording materials are discussed in Section 6.3. The Vander Lugt correlator (VLC) architecture and its variants are discussed in Section 6.4. In order to avoid the high precision required in the alignment of the spatial filter in the VLC, a novel correlator architecture was proposed and demonstrated [280]. This became known as the joint 72transform correlator (JTC) (Section 6.5). The third correlator architecture, which has been extensively explored since then, is the hybrid correlator, where significant electronic processing is involved (Section 6.6).
