| 摘要 |
PURPOSE: To obtain an optical pickup which uses a nonpolarizing beam splitter by specifying the reflectance characteristic of the nonpolarizing beam splitter. CONSTITUTION: A nonpolarizing beam splitter is used as a beam splitter by which a luminous flux toward an optical card 5 from a light source is separated from a luminous flux toward a photodetector 7 from the optical card 5. The reflectance characteristic os the nonpolarizing beam splitter is 30%<=Rave<= 80% (where Rave represents the average of a P-polarization and an S- polarization), and it is specified so as to satisfy a condition indicated by Formula (where Rp represents the reflectance of the P-polarization, Rs represents the reflectance of the S-polarization, and C represents a contrast which is defined by C=S/Po. Pa represents an average quantity of light at a time when an information pit on a card-shaped information recording medium is not detected, and S represents the difference between the average quantity of light Po and a quantity of light at a time when the information pit on the card- shaped information recording medium is not detected). |
