I've measured up this micro stepper powered lens unit to put in to the design model (taken from a Blu-ray drive sled). The plan is to use it to adjust the focusing lens by wire. For scale its about 30mm long, the arm has around 4mm travel.

In order to power it I identified the LB1935FA-AH bipolar driver as a suitable candidate. This requires x2 data lines to control rotation and one for power up (power saving & preventing unwanted adjustment), the IC is rated for 150mA and will cope with up to 8V max. I will probably run it at 3.3V with 5V signals. The motor coils have a resistance of 22.5 Ohms.

The unit includes an opto position sensor (left group of 4 pins) so once the number of steps is established, it can be easily zero'd.

So a total of 4 data IO lines required to run it properly.

Solidworks model - see files section (don't use without double checking)