Multifocal Signal Detection System Research And Design

All-field electroretinogram (ERG) can only estimate the ruction of retina in total, at the same time, local-field ERG can only test a small region of retina every time. Multifocal ERG(mfERG) which was developed by Sutter and Tran in 1992, can stimulate different regions of retina simultaneously and get the electrophysiological responses of the regions in very short time. The technique can be used to locate the pathological regions of retina and is an important development of the electrophysiology of vision.The thesis's aim is to explain the testing principle of the mfERG systematically and design the mfERG system through hardware circuit design and software algorithm programming. At first, the multifocal techniques which treat the retina as a multi-input-single-output system is discussed; it is applied to extract the local responses of retina from the mfERG mixture signal based on system recognition theory, the cross-corelation property of m-sequence and the fast walsh-hadamard transform. Second, the testing system's hardware circuit is designed and it is divided into two parts. One part is signal detecting circuit which is used to process signal by extracting, filtering, magnifying and isolating. The other part is simultaneous signal detecting circuit which is used to isolate the "Vertical Synchronous Signal" and capture its high level potential. At last, the testing system's software algorithm is designed and programed. The "Vertical Synchronous Signal" is appled to simultaneously control the m-sequence's shift and the multifocal picture's overturn to stimulate the retina. The "Double Buffer" Sampling model is applied to sample the mfERG mixture signal continuously and the "Vertical Synchronous Signal" is applied to divide the sampled signal based on m-sequence's step interval. The fast extracting algorithm together with multifocal stimulation compensation is applied to extract the response of each region. Then the testing results are displayed by different modes and saved by proper methods.The thesis combines the multifocal theory with computer data sampling and processing techniques and finishes the rearch and design of the mutifocal...