| 摘要 |
PROBLEM TO BE SOLVED: To reduce not only axial chromatic aberration but also chromatic difference of magnification to reduce chromatic aberration appearing on a screen as a whole, with respect to an objective lens for imaging having a diffraction grating. SOLUTION: The objective lens for imaging which is provided with the diffraction grating on at least one face, and the diffraction grating satisfiesϕ(r)=M×(a1r<SP>2</SP>+a2r<SP>4</SP>+a3r<SP>6</SP>+a4r<SP>8</SP>+a5r<SP>10</SP>+a6r<SP>12</SP>+a7r<SP>14</SP>+a8r<SP>16</SP>+a9r<SP>18</SP>+a10r<SP>20</SP>) wherein:ϕis a phase function; r is a length in a diametral direction of the objective lens; a1 to a10 are phase function coefficients; and -320≤a1≤-240 is true. COPYRIGHT: (C)2008,JPO&INPIT
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