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Accuracy

In this section we want to examine which factors influence the accuracy of the system. For this, we have to examine errors that can occur during the measurement of $t_\mathrm{beam}$ and $t_\mathrm{turn}$. From a measurement point of view the two are identical, since they are both an amount of time elapsed between two beam sightings. Therefore we will use $t$ as a genus for the two and $\Delta t$ as the absolute error of $t$. The following list contains possible causes for measurement errors:

In our prototype systems, the clearly dominating errors are caused by vibrations, limited $t_\mathrm{mirror}$, and flutter of platform rotation. The use of deflectable MEMS mirrors can both drastically reduce vibrations and $t_\mathrm{mirror}$. The flutter of platform rotation can be reduced to about 0.01% by using electronically stabilized motors as used, for example, in turntable drives. By this, we expect a possible reduction of $\Delta t$ by a factor of about 10.

Note, however, that the errors resulting from these three main sources can be modeled by a Gaussian noise source. This means that averaging over a large number of measurements helps to reduce the error.


next up previous
Next: Range Up: System Analysis Previous: System Analysis
Kay Roemer 2003-02-26