| 摘要 |
PURPOSE: An objective lens, a condensing optical system, an optical pickup device, and a recoding and reproducing device are provided to obtain the objective lens for recording and reproducing the information of an optical information recording medium whose diameter is small and whose working distance is large even though the lens is an objective lens with two positive lens and high NA. CONSTITUTION: An objective lens(6) is used for recording and reproducing the information of the optical information recording medium, and comprises a first lens group(6a) having positive refractive power and a second lens group(6b) having positive refractive power arranged in order from a light source side. The objective lens is a finite conjugate type lens for condensing divergent luminous flux from a light source(1) on the information recording surface(7') of the optical information recording medium, and the objective lens satisfies NA>=0.65. Then, the objective lens satisfies 0.10<=NAxWD/f<=0.35 or 0.01<= absolute value of m <=0.30.
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