| 摘要 |
PURPOSE:To vary the focal length of a lens at a high speed by providing a transparent electrode film whose resistivity distribution is proportional to the square of the distance from a specific point on one of facing surfaces of light transmissive material on the surface. CONSTITUTION:A negative crystal-axis direction is made coincident with the propagation direction of light and an electrode is provided with transparent electrode films in parallel plane shapes 22 and 23. Then, the transparent electrode film whose resistivity rho(r) is expressed by rho(r)=Cr<3> (C; constant) at distance (r) from the point 25 is provided on the parallel plane 22. A voltage V0 is applied between the point 25 and a part with a radius (a) centering on the point, and a good conductor 24. Consequently, the limit of the focus variation speed of the vari-focal lens is determined by the product of the resistance and capacitance of the electrode film to speed up the focus variation sufficiently. |
