| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical head having high utilization efficiency of light in a structure equipped with a light source with plural wave lengths and a diffraction optical device capable of coping with information recording medium of a plurality of kinds. SOLUTION: Light emitted from a light source 1 selectively emitting light with a primary wave length and light with a secondary wave-length nearly two times as long are made parallel by a diffraction type collimeter lens 3, are raised by a raising mirror 15, and then are condensed on an information recording medium 11 by a diffraction type objective lens 4. These diffraction type lenses 3, 4 emit substantially secondary diffraction light to the light with the primary wave length, and emit substantially the primary diffraction light to the light with the secondary wave length. |
