Optic fiber shutter apparatus

Abstract

An apparatus for selectively shuttering a light aperture or channel which includes a shutter blade that is rapidly moved by magnetic force between spaced apart end positions. The shutter apparatus maintains the shutter blade stable in either of the two end positions by magnetic attraction, and preferably provides a third stable position for the shutter blade which is intermediate the two end positions, such that the shutter blade has three stable positions corresponding to full, partial and no shuttering of the aperture or channel. In one embodiment, the shutter blade is part of a flag carried by a torsion beam which is fixed at one end in a mount in a cantilever arrangement, and is free to twist about its longitudinal axis. An elongated permanent magnet extends transverse to the flag and presents poles of opposite polarity. An electromagnetic system effects the movement of the elongated permanent magnet, and hence the selective movement of the flag and shutter blade, by attracting and/or repelling the permanent magnet between two end stops. The electromagnetic system includes an E-shaped pole piece of ferromagnetic material which presents three poles. The two outermost poles each have an electrically conductive winding thereon, thereby forming first and second electromagnets. The middle and salient pole is equidistant between the end poles and facilitates the movement of the permanent magnet.