Patent ID: 7755063

Claim:
An apparatus for irradiating a selected region of a target material in order to excite members of a species contained in said region to lead to a measurable effect, comprising: a source of a first radiation adapted to excite said members of said species to lead to said measurable effect; a lens adapted to focus a portion of said first radiation to said selected region so that it forms at least one maximum in said region; a source for generating a second radiation adapted to reduce the measurable effect produced by excitation of said members by said first radiation, said second radiation having at least two beam portions; and an optical assembly for directing said at least two beam portions to said region so that said portions pass through said lens, and are focused to the location of said at least one maximum in said region so that said beam portions overlap at said location, wherein said beam portions arrive at said location with a phase difference which causes the intensity of the beam portions, when overlapped at said location, to be less than the sum of the intensities of each beam portion individually in the absence of the other, and so that said location is at a minimum of said second radiation at said selected region.