OBJECTIVE LENS FOR OPTICAL INFORMATION RECORDING, REPRODUCING, DEVICE AND OPTICAL INFORMATION RECORDING, REPRODUCING, DEVICE

摘要

PROBLEM TO BE SOLVED: To form a satisfactory spot suppressing spherical aberration on a recording surface of each optical disk even if recording or reproducing information to/from three kinds of optical disks using a plurality of luminous fluxes and to suppress reduction of a focusing function when an optical disk having relatively low recording density is used.

SOLUTION: An objective lens for an optical information recording and reproducing device includes a phase shift structure having a plurality of concentric refractive surfaces in a first region of at least any one surface where a luminous flux having a third wavelength is converged on a recording surface of a third optical disk. The objective lens is made of material with an Abbe number νd satisfying a condition 40≤νd≤80. The phase shift structure has a step between each couple of the adjacent refractive surfaces that gives an optical path difference to an incident luminous flux, so that a condition 2N+1<¾ΔOPD/λ1¾<2N+1.3 is satisfied, where ΔOPD represents the optical path difference that the step gives to a luminous flux having a first wavelength and N represents an integer of zero or more.

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