Accurate time delay estimation between signals is crucial for coherent imaging systems such as Synthetic Aperture Sonar (SAS) and Synthetic Aperture Radar (SAR). In such systems, time delay estimates resulting from the crosscorrelation of complex signals are commonly used to generate navigation and scene height measurements. In the presence of noise, the time delay estimates can be ambiguous, containing errors corresponding to an integer number of phase wraps. These ambiguities cause navigation and bathymetry errors and reduce the quality of synthetic aperture imagery.In this paper, an algorithm is introduced for detection and correction of phase wrap errors. The random sample consensus (RANSAC) algorithm is used to fit one-and two-dimensional models to the ambiguous time delay estimates made in the time delay estimation step of redundant phase centre (RPC) micro-navigation. Phase wrap errors are then corrected by re-calculating the phase wrap number using the best-fitting model.The approach is demonstrated using data collected by the 270 -330 kHz SAS of the NATO Centre for Maritime Research and Experimentation (CMRE) Minehunting Unmanned underwater vehicle for Shallow water Covert LittoralExpeditions (MUSCLE). Systems with lower fractional bandwidth were emulated by windowing the bandwidth of the signals to increase the occurrence of phase wrap errors. The time delay estimates were refined using both the RANSAC algorithms using one-and two-dimensional models and the commonly used branch-cuts method. Following qualitative assessment of the smoothness of the full-bandwidth time delay estimates after application of these three methods, the results from the 2D RANSAC method were chosen as the reference time delay estimates. Comparison with the reference estimates shows that the 1D and 2D RANSAC methods out-perform the branch-cuts method, with improvements of 29 -125% and 30 -150% respectively compared to 16 -134% for the branch-cuts method for this dataset.

Using rapid thermal processing (RTP) we recently demonstrated the production of high quality well ordered barium ferrite films in times much shorter than those required by a conventional annealing process. Influence over the magnetic and structural properties developed in annealed samples was also achieved by variation of the RTP heating profile (R. Carey, P. A. Gago-Sandoval, D. M. Newman, and B. W. J. Thomas, presented at Intermag-93, Stockholm, April 13–16, 1993). It is known that the magneto-optic properties of barium ferrite can be enhanced by selective substitution of some of the Fe by Co2+ and Ti4+ albeit at the expense of reducing the magnetic anisotropy. A multitarget scanning cosputtering process has been used in conjunction with rapid thermal processing to produce a series of barium ferrite films in which Co, Cr, Mn, Ni are selectively introduced to substitute for between 5 and 20 at. % of the Fe. A corresponding percentage of Ti is also added to maintain charge compensation. The magnetic and magneto-optic properties of these films are presented and discussed with reference to their composition and treatment respect to the properties of barium ferrite.

With the continued advance in the design and production of small solid state lasers and associated optics, future systems designed to achieve very-high-density storage of digital information are likely to become increasingly dependent on sophisticated optical technology. Non-erasable storage systems that have been accepted for many years (WORM, CD-ROM and so on) show a continuous growth of applications and sales. The first erasable storage systems, produced and marketed to an agreed world standard, are firmly based on magneto-optic recording technology. This review is intended to summarize the systems and materials that have made this technology possible.

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Linear magnetic birefringence in ferromagnetic thin films in the Voigt configuration leads to intensity modulation of the transmitted radiation during hard-axis switching.Errors in the classical theory proposed by Lissberger and Parker (1971) are corrected, and the revised theory is used to calculate the magnitude of this modulation and the magneto-optic parameters Q(=Q1-iQ2) and f(=f1-if2) used in the phenomenological description of this second-order magneto-optic effect. The results are, in general, at variance with previously reported values but are both self-consistent and in good agreement with the available experimental data.