| 摘要 |
<p>The variable aperture optical diaphragm is for photographic equipment esp. for TV cameras. The diaphragm is based on the use of liquid crystal cells rendered opaque or transparent by electromagnetic excitation. The cells are rectangular in plan, are used in pairs (11a,11b,11c,11d) and may vary in number from one diaphragm design to another, lying linearly across the aperture or angularly displaced to provide an approximately circular aperture. The pairs of cells are positioned to each side of a square frame (11) leaving a fixed aperture at the centre. When used with a TV camera the cell group is situated between the elements of the lens. The pairs of cells are controlled by a coded switching circuit powered from a battery. Feedback from the video signal compared with a reference voltage provides the switching circuit control.</p> |
