| 摘要 |
PURPOSE:To detect a reflection light having no false signal with good efficiency by condensing the light from a semiconductor laser on an optical disk via a condensing grating coupler (GC), waveguide path and two piece condensing GC, and distributing the reflection light to an optical detecting element by the two piece GC. CONSTITUTION:The laser light incident through a substrate 11 from a semiconductor laser element 8 is guided to the optical path inside a wave guide path 12 from a condensing GC 13 and condensed on the information recording face 6a of an optical disk 6 through the end face 11a subjected to no reflection coating via the two piece condensing GC 15 and condensing GC 14 whose diffraction efficiencies are adjusted in about 50%. The reflection light light thereof is halved by the two piece condensing GC 15 with its retrograde and made incident on four optical detecting elements 16a-16d. In the case of the focusing being normal, the detection outputs of the elements 16a-16d become equal. A focusing error signal is obtd. by detecting the break of the output ratio. A tracking error signal is obtd. from the ratio of the sum of the elements 16a, 16b and 16c, 16d. |
