| 摘要 |
PURPOSE:To simplify the mechanism of a focusing detecting device, and in its turn of a video camera, and to reduce the size and price of the device by changing the distance between transparent plates and the optical path length of a video lens, i.e. the optical distance only by impressing voltages to piezo-electric elements. CONSTITUTION:When AC voltages with reverse phases respectively are impressed to the piezo-electric elements 6, 7 and 8, 9 fitted to the front and back surfaces of a variable optical length plate, the elements 6, 7 and 8, 9 are expanded/contracted respectively in the reverse directions to drive the aperture parts of U-shaped plates 3, 4 respectively in the opening and closing directions. Since the AC voltages are impressed to the elements 6, 7 and 8, 9 so that transparent plates 1, 2 adhering to the insides of the aperture parts are separated/ approached in parallel. When the distance between the transparent plates 1, 2, i.e. the thickness of a liquid layer 5, is thinned, the transparent liquid 5 is leaked from the outer edges of the plates 1, 2. Thereby, chambering parts are formed on the insides of the outer edge parts of the plates 1, 20 to prevent the liquid 5 from being leaked by surface tension. Thus, the mechanism can be simplified. |
