PURPOSE: To rapidly control the focus, without having mechanical movable parts, by forming the lens part in a substrate having an electro-optics effect in an united body, and then providing an electrode so as to surround the lens part, and impressing a voltage to the electrode.

CONSTITUTION: The lens part 11 having a gradient of a refractive index is buried in the substrate 10 composed of the material having the electro-optics effect to form the titled lens. The positive and negative electrodes 12A and 12B are arranged on the substrate so as to surround the lens parts 11. LiNbO3 is used to the substrate 1. The lens parts 11 gradually reduces the distribution of the refractive index toward the deep part from the surface of the lens, and has a semicircular in a cross sectional form of the lens. If the electric field is impressed to the electrodes 12A, 12B respectively, a light is gathered to the focus 14A. If the electric field is impressed to the electrodes, the refractive index at the each points of the lens parts 11 changes by the electro-optics effect whereby the focus moves to 14B. Accordingly, as the position of the focus is controlled by changing the voltage of the electrode provided at the side edge part of the lens, the focus may be rapidly controlled. So that the titled lens is useful for writing an optical disc information.