| 摘要 |
There is provided an optical head including a laser diode chip, a lens for focusing lights onto an object, an optical separator for separating lights reflected from the object, from an optical axis of a light directing towards the lens from the laser diode chip, and a photodiode chip receiving lights having been separated from the optical axis by the optical separator. The optical separator is defined by first and second sidewalls, and first to fourth outer surfaces, and has first and second inner planes both being inclined relative to the first outer surface. A light enters the first outer surface, passes through the first and second inner planes, leaves the optical separator at the third outer surface, and is focused onto the object by the lens. The light having been reflected by the object enters the third outer surface, and is reflected at the second inner plane by the remaining half. The light having been reflected at the second inner plane is received in a front light-receiving section formed on the light-receiving plane. The light having passed through the second inner plane is reflected at the first inner plane, and is received in a rear light-receiving section formed on the light-receiving plane. The laser diode chip is positioned so that an optical length between the laser diode chip and the first inner plane is equal to (a+b-c)/2 wherein "a" indicates an optical length between the first inner plane and said rear light-receiving section, "b" indicates an optical length between the second inner plane and the front light-receiving section, and "c" indicates an optical length between the first and second inner planes.
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