| 摘要 |
PURPOSE:To obtain a lens which can largely vary a focal distance at a high speed by providing a case formed by covering both apertures of a cylindrical body with expandable and contractable transparent films in parallel, light pervious liquid filled in the case and a piezo-electric material control means for impressing a voltage to a piezo-electric material. CONSTITUTION:The transparent films 2 consisting of, for example, polyester are spread on the parallel front and rear faces of the doughnut-shaped piezo-electric cylindrical case 1 which is constituted of a ceramic piezo-electric element or the like and is vertically hollowed throughout the case to hermetically close the inside thereof and the high refractive index liquid 3 such as, for example, toluene, is filled therein. The volume in the case 1 decreases and the transparent films 2 change to a projecting shape when the voltage is impressed to the electrode 5 of the case 1 by using a power supply 4. The liquid in the case 1 works, so that the case 1 acts as a lens. The lens which largely varies the focal distance at a high speed is thereby obtd.
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