Development of a parallel access optical disk system for high speed pattern recognition
Pattern recognition is a rapidly expanding area of research, with applications ranging from character recognition and component inspection to robotic guidance and military reconnaissance. The basic principle of image recognition is that of comparing the unknown image with many known reference images or 'filters', until a match is found. By comparing the unknown image with a large data bank of filters, the diversity of the application can be extended. The work presented in this thesis details the practical development of an optical disk based memory system as applied in various optical correlators for pattern recognition purposes. The characteristics of the holographic optical disk as a storage medium are investigated in terms of information capacity and signal to noise ratio, where a fully automated opto-mechanical system has been developed for the control of the optical disk and the processing of the information recorded. A liquid crystal television has been used as a Spatial Light Modulator for inputting the image data, and as such, the device characteristics have been considered with regard to processing both amplitude and phase information. Three main configurations of optical correlator have been applied, specifically an image plane correlator, a VanderLugt correlator, and an Anamorphic correlator. Character recognition has been used to demonstrate correlator performance, where simple matched filtering has been applied, subsequent to which, an improvement in class discrimination has been demonstrated with the application of the Minimum Average Correlation Energy filter. The information processing rate obtained as a result of applying 2D parallel processing has been shown to be many orders of magnitude larger than that available with comparable serial based digital systems.