- Spectrum analysis has been shown as one of the most useful techniques in modern science. Virtually every discipline makes use of it in one form or another. Generally, spectrum analysis has been performed by electronic systems. However, due to the fundamental simplicity, parallelism and intrinsic speed of optical processing systems, the usefulness of optical spectrum analysis has grown remarkably in the past decade. These features of the optical system offer an alternative in designing spectrum analyzers for temporal signals. This thesis describes various designs of optical spectrum analyzer for temporal signals, especially for those signals within the audio frequency range.
Since the processing of temporal signal by optical means necessitates the transformation of the signals to spatial formats, different temporal-to-spatial signal conversion techniques are reviewed. The general characteristics of recording media used in the signal conversion process are discussed.
The designs of time-signal optical spectrum analyzers are classified as on-line (real-time) and off-line (non-real-time) spectrum analyzers based on the recording medium used in temporal-to-spatial conversion process. Three different types of optical spectrum analyzers in off-line case are described. The design of a continuous single channel spectrum analyzer is emphasized because of its simplicity and suitability for the signal of interest. In addition, a white-light optical spectrum analyzer operated under partially coherent mode is designed and evaluated. The spectrograms generated from this white-light optical system are frequency color coded, which in turn, provide a better visual discrimination in the frequency contents of the signal. Moreover, a hybrid optical spectrum analyzer is synthesized for an on-line case by means of a real-time image converter, LCLV, in conjunction with a home-built digital electronic control circuit. The feasibility of a real-time optical spectrum analyzer is also studied.
Human speech signals together with computer simulated vowels are used as test signals in demonstrating the experimental usage of the designed systems. Several spectrograms are provided in different cases. Results obtained from digital processing (FFT) using similar techniques for the same signals are also presented for comparison.
- Dissertation Note:
- Ph.D. The Pennsylvania State University 1987.
- Source: Dissertation Abstracts International, Volume: 48-04, Section: B, page: 1117.
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