Patent ID: 8439581

Claim:
A method of controlling a plurality of shutter blades, comprising: a) providing a shutter assembly including: a drive ring having first and second oppositely-facing sides, at least one shutter blade of the plurality of shutter blades being movably coupled to the first side, a first permanent magnet coupled to the second side of the drive ring, a first solenoid selectively energizable to alternately attract and repel the first permanent magnet along an arcuate path beneath the first solenoid, and a sensor assembly configured to detect a change in distance between the sensor assembly and the first permanent magnet as the first permanent magnet moves along the path; b) moving the plurality of shutter blades between an open position exposing a central opening of the shutter assembly and a closed position; c) sensing the change in distance between the first permanent magnet and the sensor assembly as the first permanent magnet moves along the path; and d) reducing an electrical signal applied to the first solenoid, while the plurality of shutter blades is in transit between the open and closed positions, in response to the sensed change in distance.