OPTICAL DEVICE

摘要

PROBLEM TO BE SOLVED: To use the same light receiving element for detecting a reflected luminous flux from an information recording medium and to reduce the area of the light receiving element. SOLUTION: A luminous flux 8 exited from a semiconductor laser element 1 and a luminous flux 9 exited from a semiconductor laser element 2 are condensed/reflected on/from the information recording medium 4 by an objective lens 3 being a condensing means, and again are made incident on a hologram element 5 being a luminous flux branching means via the objective lens 3. The luminous fluxes from the information recording medium 4 are diffracted in the X direction in the figure by the hologram element 5, and the 1st-order diffracted light are guided to the light receiving element 7.