| 摘要 |
PURPOSE:To make the titled pickup light and small-sized by using the converging diffraction grating (FGC) formed on an optical wave guide path. CONSTITUTION:An optical beam 15 is focused on the reflection face of a recording medium 13 by the 1st FGC 17 provided on a 1st optical wave guide path 22 and by fetching a reflection beam 15' into 2nd or 3rd optical wave guide path by 2nd-4th FGC 31-33 the reflection beam 15' is guided to an optical detector side. The FGC 31-33 focus the reflection beam 15' in the 2nd or 3rd optical wave guide path. Since the FGC 31, 32 are arranged, the reflection beam 15' is separated in the tracking direction each other and focused at two places. The FGC 31, 32 excites a TE(TM) wave guide mode and on the other hand the FGC 33 excites a TM(TE) wave guide mode, so the output of the 1st and/or 2nd optical detector 24, 25 and that of the 3rd optical detector 26 are complimentarily varied and the recording information can be read by detecting the difference in the outputs of two sets. |
