| 摘要 |
<p>Provided are an optical pickup device with objective lens, an optical information recorder / player, and an objective lens optimal for use therein which, despite a relatively short focal length, ensure the working distance of a CD, keep away unnecessary diffracted light prone to result in error signals, and, while further having good off-axis characteristics, are capable of achieving compatibility with three types of optical discs, BDs, DVDs and CDs, with a common objective lens. If the value of formula (5) is greater than or equal to the lower limit, unnecessary light of a 1/1/1 structure can be kept away, erroneous detections detected by an optical detector along with the main light can be suppressed, and further, sufficient working distance suitable for CDs can be ensured. Meanwhile, if the value of formula (5) is less than or equal to the upper limit, the difference between the sine conditions during BD use and during CD use lessens, and off-axis characteristics during CD use can be improved. Further, in combinations of 1/1/1 and 2/1/1 structures, by fulfilling these conditional expressions, axial chromatic aberration in BDs can be reduced. 0.04 = (fB3-fB1)/d = 0.12 (5), wherein fB1 = WD1+t1×(1-1/n1), fB3 = WD3+t3×(1-1/n3), and d is the thickness on the axis of the objective lens (mm).</p> |
