| 摘要 |
In an embodiment, an optical pickup includes at least one light source for selectively emitting three light beams having blue, red, and infrared wavelengths, respectively, and an objective lens arranged so that each of the three light beams enters thereto. The objective lens includes a first grating, and a second grating formed in the same plane as the first grating. The first and second gratings each have phase steps arranged concentrically around a center axis of a lens in a region in which all the three light beams pass, and are different in phase step positions. The first grating diffracts the three light beams having the blue, red, and infrared wavelengths in a 2nd order, a 1st order, and the 1st order, respectively. On the other hand, the second grating diffracts the three light beams having the blue, red, and infrared wavelengths in the 1st order, the 1st order, and the 1st order, respectively. As a result, the three light beams having the blue, red, and infrared wavelengths, which have been transmitted through the first grating and the second grating, are diffracted in a 3rd order, the 2nd order, and the 2nd order, respectively.
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