Are interferometric encoders a reasonable alternative in servo drive applications?

In 2005 and 2006 there have been publications explaining the technical requirements of encoders to be used in electrical drives with digital control. The main statement of these papers have been that neither high resolution resolvers nor high resolution optical encoders really do provide features as good as of analogue tacho generators. The performance of servo drives with digital control, however, has improved in comparison to former drives with analogue control. Nevertheless the speed detection performance of optical encoders still cannot cope with high precision tacho generators - they still are the technical bottle neck for further improvements in digital drive control. This paper reports on some development in the field of interferometric encoders, which, provide a significant higher resolution than optical encoders. Technical results obtained by some initiative research indicate, that interferometric encoders have a good potential and should investigated more further on.