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K U Plagwitz

Publications and source records attributed to K U Plagwitz.

5 recordsLinked to original sources
PubMed2002

[Improving SNR (signal to noise ratio) in multichannel EEG recording].

The main problem in measurements of the focal VEP (Visual Evoked Potential) is its weak SNR (Signal-to-Noise Ratio). The most common method for enhancement of the SNR is the stimulus synchronized averaging. For study of single responses other ways in SNR improvement are needed. In this contribution a new method based on space-time selective measurement is introduced, which can be interpreted as beaming a signal source. Since the anatomical structures of sources generating the focal VEP are known in general and if the electrode positions are of sufficient density over the visual cortex, a source beamer can be realized by controlling the channels' delays.

Algorithms↗
PubMed1999

[New measuring method of non-contact tonometry].

BACKGROUND: The measuring value of intraocular pressure (IOP) in non-contact-tonometry (NCT) depends on IOP and is additionally highly influenced by the biomechanical parameters of the cornea. These parameters (especially corneal thickness) differ among several patients. It is desirable to characterize this influence and to correct the measuring value during the IOP measurement. The new tonometer consists of an air pulse applicator generating an air pulse with a rampshaped rising and a sharp decay after switching off and a Michelson-type laserinterferometer for detecting the corneal movement during the air pulse application and the oscillation after switching off the air pulse. METHOD: The method was tested with a mechanical phantom eye. The pressure inside the chamber of the phanton is adjustable. Measuring surfaces, which have to simulate the shape and the elastic properties of the cornea, are made of soft silicon rubber and fabricated with different thicknesses. RESULTS: Measurement results show that both the rise of the corneal deformation and the damped oscillation (frequency and damping) depend from material thickness and internal pressure of the phantom eye. CONCLUSION: Thus a characterization of the influence of the mechanical properties and a determination of a corrected IOP-value are possible. The task at present is the investigation and formulation of the mathematical dependences.

Corneal Diseases↗