sourcing miniature epicylics/planetarys

re: minature epicyclics for rack-and-pinion to rotary encoder

Accuracy of gear-on-rotary encoders running along a rack
can be improved perhaps by mounting a miniature epicyclic
between the encoder and gear (to increase the encoder shaft
rotation relative to the gear rotation).

Anyone seen such a unit? (part numbers/web addresses please,
not just vague Berg/SDP/mcmastercarr/Boston Gear/Dayco/
Grainger/etc suggestions).

Anyone tried this? For instance a 32 pitch 0.5" PD spur gear
travels 1.570795"/revolution. Using a US-Digital S2 Optical
Shaft Encoder (2048 CPR) gives 0.000 766 inch per count.

Using a 7.7 : 1 ratio planetary would give approx 0.000 100
per encoder step.

Thanks
Doug

PS: The next post will tell me there will be backlash. Instead of
telling me why it won't work, try to be positive! I thought of
sandwiching a gear between two racks (one fixed, one attached
to the table). The rate of rotation of the gear is half as much,
but there is likely to be less backlash and way less radial force
on the encoder shaft. This arrangement will allow a much
higher planetary gear ratio as well (say 10 or more).