Patent ID: 7227704

Claim:
An objective lens module comprising: a light-converging lens that is coaxially disposed with respect to an optical axis of first laser light having a first wavelength; and a transmission-type diffractive optical element that is coaxially disposed to cause diffracted light of first laser light to be incident on the light-converging lens, wherein the diffractive optical element has: an incident surface and an emergent surface; and first, second, and third regions that are provided on at least of the incident surface and the emergent surface in the vicinity of the optical axis, and are sequentially defined according to different radius distances from the optical axis to have different diffraction gratings of different diffraction angles, respectively, and the first region diffracts odd-order diffracted light of first laser light to the light-converging lens, the second region diffracts even-order diffracted light of first laser light to the light-converging lens, and the third region diffracts even-order or zero-order diffracted light of first laser light to the light-converging lens, such that the light-converging lens converges diffracted light from the first, second, and third regions with a predetermined numerical aperture.