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US 7,924,419 B2Granted
Illumination system for optical inspection
AssigneesApplied Materials Israel Ltd., Applied Materials, Inc.
InventorsRon Naftali, Avishay Guetta, Haim Feldman, Doron Shoham
Life of this patent
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Abstract
Apparatus for generating optical radiation includes a laser, which is configured to operate in multiple transverse modes simultaneously so as to generate an input beam, which is characterized by a first speckle contrast. The transverse modes of the input beam are optically mixed so as to generate an output beam have a second speckle contrast, which is substantially less than the first speckle contrast.
Claims6
An apparatus for reducing speckle in a beam of laser radiation, comprising:
- an optical scanner configured to deflect a portion of the beam by diffraction and to scan an incidence angle of the deflected portion of the beam over a range of angles using an acousto-optic transducer and a drive circuit coupled thereto, wherein the beam is a pulsed beam, and the drive circuit applies a frequency-chirped pulse to the acousto-optic transducer in synchronization with the pulsed beam to diffract a first order of the beam and to scan the deflected portion of the beam on a target plane at an angle that varies over a duration of the laser pulse;
- and
- output optics, which are coupled to direct the deflected portion of the beam exiting from the scanner so that the beam irradiates a single area of the target plane over a range of different angles, so as to de-correlate the radiation, the output optics including a lens and a diaphragm at a Fourier plane of the lens to stop an undeflected zero order of the beam from passing.
A method for reducing speckle in a beam of laser radiation, comprising:
- optically scanning the beam to deflect a portion of the beam by diffraction and to scan an incidence angle of the deflected portion of the beam over a range of angles using an acousto-optic transducer and a drive circuit coupled thereto, wherein the beam is a pulsed beam, and the drive circuit applies a frequency-chirped pulse to the acousto-optic transducer in synchronization with the pulsed beam to diffract a first order of the beam and to scan the deflected portion of the beam on a target plane at an angle that varies over a duration of the laser pulse;
- and
- directing the portion of the beam through output optics including a lens and a diaphragm at a Fourier plane of the lens so that the beam irradiates a single area of the target plane over a range of different angles, so as to de-correlate the radiation, the diaphragm stopping an undeflected zero order of the beam from passing.
Dependencies are inferred from the claim text.