The Application Of Periodic Complementary Sequence In Extracting Multifocal Visual Evoked Potential

The multifocal visaul electrophysiology check technique is developed in recent years , which can examine several retina districts simultaneously, shorten the check time, and can compare the function of different part of retina. It not only has very important value for clinical applying and for exploring and researching the visual system, but also represents international highest level and the development trend of visaul electrophysiology. It is later that research developed in our country, and has no successful instrument to be released still currently. It is restricted to this new technique for clinical application, and extremely disadvantageous to research and development of visual electrophysiology in our country, because the prices of the equipments imported are very expensive. Therefore, the research of examination equipments for mfERG (multifocal electroretinogram) Be going necessarily. In addition, that technique has good exploitation value for extracting response signal of different district in plane target from mixture signal with low amplitude and low signal-to-noise ratio.The signal of mfERG is very weak (<1μ V), and drowned into the strong background noice, so the examination is a very difficult work. Currently, The mfERG selects different start points from m-sequence to control stimulating different parts of retina respectively at one time, recording a mixture reaction signal, calculated through fast Walsh transform by computer, and separate the corresponding wave of each part.The control sequence is the core part of producing mfERG incitement process and analyzing the result. It must satisfy the following two conditions: â‘  the light incitement is nearly equal to the no-light incitement inside the stimulation wild at any time; â‘¡ the responding of each retina district is not related with each other(orthogonal). The m-sequence is easily satisfy the request of the condition â‘¡ by its characteristic of correlation, but we have to look for many different start points from the m-sequence in order to satisfy the condition â‘  . It is very difficult to look for tens or hundreds different starts from such a sequence as 2¹²²¹⁵ long for controlling mfERG stimulation. In addition, it certainly will influence the test result because of the auto-correlation function between each different starting point of m-sequence is not equal to zero absolutely.This paper put forward another way for producing test sequence by periodic complementary sequence to put the axe in the helve in looking-for starting points from...