METHOD FOR READING OUT OPTICAL INFORMATION

PURPOSE:To accurately control a position of an object lens for the reference plane by keeping a surface of an information pit of the reference plane in the prescribed range of a non-focus region, when information is read out of an optical recording medium. CONSTITUTION:This device is provided with a light source 11, two beam splitters 15, 17, and an object lens 19, further, is provided with a cylindrical lens 21 detecting a focusing error, a first optical detector 25, a second optical detector 27 detecting a tracking error. A light beam 12 from the light source 11 irradiates the reference plane 35 of a recording medium through the beam splitter 15 and the object lens 19, the light beam reflected by an information pit 35P of the reference plane 35 is guided to the beam splitter 17 again through the object lens and the beam splitter 15. Then, it is divided into two luminous flux 12f, 12t, the luminous flux 12f is guided to the cylindrical lens 21 and detected by the first optical detector 25, the luminous flux 12t is detected by the second optical detector 27.