OPTICAL READER

PURPOSE:To perform easily the positioning and adjustment of photodetectors and to improve detecting sensitivity by separating a part of a center part and a part of a peripheral part at least out of returning light flux from a beam splitter in different directions and guiding respective light rays to respective photodetectors. CONSTITUTION:The light flux from a semiconductor laser LD is focused like a spot on a disc D and the returning light flux reflected by the signal surface passes through an optical path reversely, turns its optical path from the deflecting beam splitter 12 to an auxiliary lens 15 side and is made incident to a space dividing half mirror 16. The light reflected on a center part 16a of the mirror 16 is made incident to a photodetector PD1 and the light passing through a peripheral part 16b is made incident to a photodetecor PD2. Consequently, the positioning of the photodetectors can be easily adjusted and the detecting sensitivity can be improved by reducing the diameter (b) of the center part 16a of the space dividing half mirror 16.