Patent ID: 7656592
Filing Date: 2010-02-02
Classification: G02B

Abstract:
1. Optical apparatus, comprising: an optical system arranged to receive a laser-beam, said laser-beam having a substantially Gaussian intensity profile, said optical system including a substantially diffraction-limited lens having a longitudinal optical axis and arranged to focus said laser-beam into a focal region having a depth extending parallel to said optical axis, wherein said focal region extends axially plus and minus four Rayleigh ranges of the focused laser beam from a nominal focal plane of said diffraction-limited lens; and wherein said optical system further includes one or more optical elements configured to introduce one or more optical aberrations into said laser-beam before said laser-beam is focused into the focal region by the diffraction-limited lens, the extent of said one or more optical aberrations introduced by said one or more aberration-introducing elements being arranged such that the intensity profile of the focused laser-beam is quasi-flat-topped at one or more paraxial positions in said focal region.