| 摘要 |
<p>An optical head device includes: light source means for emitting a laser beam for each of a plurality of types of optical discs; a first objective lens for collecting the laser beam emitted from the light source means onto a recording surface of one type of optical disc and a second objective lens for collecting the laser beam onto a recording surface of the other type of optical disc; one light reception element for receiving a signal light from the recording surface; and an optical system for introducing the laser beam into the first or the second objective lens, performing light synthesis or light separation accompanied by at least a partial reflection on the signal light according to the optical disc type and introducing the signal light to the light reception element, wherein a difference between the number Nb of reflections from the one type of optical disc to the light reception element and a number Mb of the reflections from the other type of optical disc to the light reception element is 0 or an even number.</p> |
