Electrically driven bistable mechanical actuator

Apparatus for controlling the passage of radiation, comprising:

• a shutter unit including a linearly actuated shutter arm;
• a linear actuator comprising
• an electromagnet,
• ferromagnetic plunger disposed adjacent to the electromagnet and movable with respect to the electromagnet along an actuation axis, the plunger having a first end face and a second end face,
• a first permanent magnet positioned remote from the electromagnet and in facing relation to the first end face of the plunger along the actuation axis, the first permanent magnet attracting the plunger thereto, and
• a second permanent magnet positioned remote from the electromagnet and in facing relation to the second end face of the plunger along the actuation axis, the second permanent magnet attracting the plunger thereto, the plunger being slidable along the actuation axis between a first position with the first end face adjacent to the first permanent magnet and a second position with the second end face adjacent to the second permanent magnet, the plunger being retained adjacent to one of the permanent magnets when the electromagnet is not energized;
• a bipolar electrical DC power supply operatively connected to the electromagnet;
• and
• a push rod mechanically connecting the plunger to the shutter arm.