MINIATURE DIFFERENTIAL DRIVES

Coarse Adjustment
The knob "A" is permanently fastened to the 1/4"-80 externally threaded Main Body "B"; this provides the coarse angular adjustment of the kinematic mount.

Fine Adjustment
The fine-adjustment (25µm/rev) is actuated by inserting a hex wrench through the clearance hole in the adjuster knob. Each rotation of the DAS110 fine-adjustment mechanism yields a highly de-magnified displacement of just 25µm.

The Main Body "B"is also internally threaded with an M3-0.40 thread, this thread holds the intermediate actuator "C", which may be rotated by a hex wrench. The key to the design is that the intermediate actuator is both internally and externally threaded allowing a differential movement to be achieved between the intermediate actuator "C" and the Push Rod "D".

The external thread of the intermediate actuator is the same M3-0.40mm thread internal to the Main Body. When the intermediate actuator is rotated clockwise, it moves out of the Main body by 400µm per revolution. Connected to the internal thread of the intermediate actuator is the Push Rod; the Push Rod mates to the intermediate actuator via a M3-0.375 thread and is restricted from rotating by the main body. Now as intermediate actuatoris rotated, it advances at the rate of 400µm/rev. but the Push Rod retreats at 375µm/rev. This results in a “differential” motion of the Push Rod that is equal to the net difference of the pitch of the two threads for total displacement of 25µm/rev.