Research And Implementation Of ERG Signal Acquisition And Processing System Based On EOG

The visual system is one of the most important systems of human perception. Diseases of the visual system seriously threaten our normal life. Many pathological changes of the visual system are gradual. Early detection and treatment is the important topic of clinical ophthalmology, preventive medicine and epidemiology. Compared to the traditionally psychological and physical examination, from the point of view of electrophysiology, Visual electrophysiological examination can realize comprehensive diagnosis of the visual pathways, provides a more suitable method for detecting early lesions of visual. Traditional visual electrophysiology includes three aspects:Electroretinography (ERG); Visual Evoked Potential (VEP); Electrooculography (EOG). Visual electrophysiology has built up clinical inspection standards. Comparatively speaking, examination of ERG has wider applications.In the past, restricted by acquisition precision of measurement equipment, signal noise ratio (SNR) of ERG signal acquired through the skin electrode is at a low level. Signal can not satisfy the criteria for clinical application. Therefore, in the traditional measurement of ERG, the corneal contact lens electrode is used to extract the retina electrical signals. However, there are many disadvantages on the use of cornea contact lens electrode, for example, patients with corneal diseases are not suitable for wear, at the same time, some patients, such as children, is not easy to cooperate to check. With the constant improvement of the accuracy of Analog to Digital Converter (ADC), acquisition of weak physiological signal can get higher SNR. This makes acquisition of ERG signal through the skin electrode possible. This thesis mainly research on the content of the following several aspects:First, this thesis expounds the background of this subject and the meaning of retinal electrophysiology research, and introduces the basic theory of visual electrophysiology, focuses on the generating mechanism of EOG and ERG signal, the basic characteristics of the signal and the detection method of signal.Second, acquisition system of ERG signal is introduced. Acquisition of ERG analog signal is implemented by designment of hardware acquisition circuit.24 bits high-precision ADC is applied in the A/D conversion of analog signal. By using high-resolution ADC, we can effectively reduce the magnification of analog front end, reduce noise figure of analog devices. So that we can get higher SNR, and the collected ERG signal can meet the requirements of clinical application.Finally, under the condition of dark adaptation, we collect signals of multiple samples and process the data of A/D conversion by the technique of digital signal processing. In addition, when we collect ERG signal through the skin electrode, the electrodes need to be placed around the eye, so in the process of acquisition, in the event of eye movement behavior or the blink of an eye, EOG will also be synchronous acquisition, therefore we should try to keep eye still. At last, we extract ERG signal from the data of acquisition and compare with standard ERG signal, in order to determine the correlation.