| 摘要 |
PURPOSE:To practically narrow the interval between photodetectors, and to improve the detecting sensitivity of a focus error signal, and to realize correct focus servo control by integrating the photodetectors of more than a pair in waveguide detecting system, and arranging the photodetectors so that each of them is shifted before and behind in the propagation direction of a waveguided light. CONSTITUTION:Reflected light from an optical disk 21 coupled and waveguided to an optical waveguide layer 17 by a grating coupler 14 is divided into two fluxes of light P, Q by a waveguide lens 18, and they go toward the photodetectors 19a, 19b and 20a, 20b at one end of a substrate 15. The photodetectors 19a, 19b and 20a, 20b to make pairs are arranged so as to be shifted before and behind respectively in the direction of the waveguided light. Thus, the intervals between the photodetectors 19a, and 19b and between the photodetectors 20a and 20b come narrow practically for the fluxes of light P, Q. Thus, the detecting sensitivity of the focus error signal is improved, and the correct focus control can be realized. |
