Using a DAC to convert digital to analog current

The word lens is just the transparent bit that does the optical focusing.
It looks to me like this is some sort of read / write head from a CD or other optical reader.
Normally with no power these will be in the center.
There are galvanometer coils that do the movement and you have to apply power to these.
I would try what lefty suggested and put out a PWM signal through a transistor or FET to increase the current. However the coils might respond to these rapid signal changes, see:-
http://www.thebox.myzen.co.uk/Tutorial/PWM.html
It could be they need smoothing.
How fast do you want to change the voltage going to those coils?
What sort of resolution do you want with the movement.