| 摘要 |
<p>A shutter mechanism having an electromagnet and a flexible ferromagnetic blade (30, 64) mounted in narrow V-shaped relationship to one another at an end opposite from a light source, with a light path (32, 66) passing between the two. The electromagnet has a cylindrical core (34, 68) with a lengthwise slice defining poles (38 and 40, 74 and 76) and a toroidal wire winding (36, 70) about the core. When the magnet is activated, the free end of the blade flexes toward the poles completing the magnetic circuit, and either opening or closing the shutter. In a normally open embodiment, the light path passes between the magnetic poles (74 and 76), and the blade (64), normally parallel to the beam path (66), flexes downward to block the beam. In a normally closed embodiment, when the blade (30) flexes the light path (32) passes through a slot (52) in a backup plate (46) against which the blade normally rests. The normally closed embodiment includes a light absorptive tongue (54) between the poles (38 and 40) which combines with the reflective blade to define a light trap. In the normally open embodiment, the blade combines with a light absorptive slotless backup plate (80) to define the light trap.</p> |
