| 摘要 |
PROBLEM TO BE SOLVED: To realize an inexpensive optical disk device excellent in interchangeability by realizing an objective lens and an optical head capable of CD reproducing, CD-R recording and reproducing, DVD-ROM reproducing and DVD-RAM recording and reproducing. SOLUTION: By changing the thickness of corresponding substrates on the inside and the outside of this objective lens and providing a projected circular phase shifter 32 at a center part and a zonal phase shifter 31 at the peripheral part of the shifter 32, aberration caused in a DVD whose substrate thickness is 0.6 mm and aberration caused in a CD whose substrate thickness is 1.2 mm are decreased. Then, aberration in CD reproducing is decreased further and NA(numerical aperture) is increased to 0.5 so as to realize CD-R recording. |
