To obtain a high numerical aperture objective lens whose numerical aperture is large and which is provided with excellent performance though it can be comparatively easily manufactured and it is inexpensive by providing a first and a second lens elements with an identical surface profile.
The high numerical aperture objective lens 10 for focusing a laser beam is constituted of the first lens element 12 through which the laser beam is passed and whose optical magnification is positive and the second lens element 14 which is adjacent to the element 12 and whose optical magnification is positive. It is preferable that the refractive index of the elements 12 and 14 is 1.7 or ≥1.7. When the refractive index is high, the higher numerical aperture is easily attained. The elements 12 and 14 are positioned so that they are approached and combined each other. Then, the lens 10 whose numerical aperture is 0.83 is formed of the elements 12 and 14. Besides, the elements 12 and 14 of the lens 10 are provided with the identical surface profile.
PHILIP D BAADEJJI
PAUL O MCLOUGHLIN
DAVID A RICHARDS
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