| 摘要 |
There is provided an objective lens including a first optical member and a second optical member which are made of materials different from each other and are cemented together at a cementing surface. The cementing surface includes a first phase shift structure having a plurality of refractive surface zones concentrically formed about an optical axis of the objective lens. The first phase shift structure satisfies conditions (1) and (2): <?in-line-formulae description="In-line Formulae" end="lead"?>0.85<Phi2/Phi1<1.15 (1)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>0.10<|Phi3-Phi2)/Phi1|<0.50 (2)<?in-line-formulae description="In-line Formulae" end="tail"?> where Phi1=m(lambda<SUB>1</SUB>)x(lambda<SUB>1</SUB>/(n2(lambda<SUB>1</SUB>)-n1(lambda<SUB>1</SUB>))), Phi2=m(lambda<SUB>2</SUB>)x(lambda<SUB>2</SUB>/(n2(lambda<SUB>2</SUB>)-n1(lambda<SUB>2</SUB>))), Phi3=m(lambda<SUB>3</SUB>)x(lambda<SUB>3</SUB>/(n2(lambda<SUB>3</SUB>)-n1(lambda<SUB>3</SUB>))), m(lambda<SUB>1</SUB>), m(lambda<SUB>2</SUB>), and m(lambda<SUB>3</SUB>) are diffraction orders at which diffraction efficiencies of the first through third light beams are maximized, respectively, n1(lambda<SUB>1</SUB>), n1(lambda<SUB>2</SUB>), and n1(lambda<SUB>3</SUB>) are refractive indexes of the first optical member, respectively, and n2(lambda<SUB>1</SUB>), n2(lambda<SUB>2</SUB>), and n2(lambda<SUB>3</SUB>) are refractive indexes of the second optical member, respectively.
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