It is known in the art to provide a shutter mechanism for moving a shutter blade, or a filter element or other such component, between spaced apart first and second end positions by magnetic force. For instance, electromagnets have been used to move a shutter blade between a first position which allows light to pass through an unshuttered aperture, to a second position which prevents the passage of light through the aperture.
Such known shutter mechanisms operate to fully cover or fully uncover the aperture, and are not adapted or even desired to provide a third position in which the aperture may only be partly covered (a half attenuation mode). Further, such prior art devices are ordinarily fairly large, and are not designed to operate at a rate of many cycles a second.
USPTO Backgrounds
USPTO Backgrounds