Processor for optical information

PURPOSE:To form the spot of all directions on the disc efficiently and to enable to increase the range of automatic focus drawing, by increasing the numerical aperture of coupling lens and locating the prism at the post stage of the coupling lens. CONSTITUTION:To the semiconductor laser element 1 having non-isotropic spread angle, the coupling lens has greate automatic focussing drawing range to greater numberical aperture allowing to realize perfect automatic focussing to the up and down movement of the disc 4. Then, by using the coupling lens 2 having greater numerical aperture and inserting the prism 7 immediately after the coupling lens 2, the conversion of isotropic beam can be made. This light beam can obtain the isotropic spot 5 on the disc 4 by means of the objective lens 3, and since the numerical aperture of the coupling lens 2 is taken greater, the feedback of reflection light to the semiconductor laser 1 is greater, allowing to extend the range of automatic focus drawing.