Optical: systems and elements – Diffraction – From grating
Patent
1998-07-09
2000-06-06
Spyrou, Cassandra
Optical: systems and elements
Diffraction
From grating
359575, 359565, G02B 518
Patent
active
060726318
ABSTRACT:
A diffractive homogenizer is provided for receiving a beam of laser energy and producing a desired illumination pattern in a target plane. The homogenizer is made up of a plurality of diffractive sub-elements, each of which contributes to all or a portion of the desired image. By combining the contributions of many sub-elements to form the final image, a homogenizing effect is realized. In preferred embodiments, the sub-elements are designed to compensate for the finite spatial coherence of the incident laser beam and to control the numerical aperture distribution of the transmitted light. Each sub-element is composed of a large number of discrete pixels, each of which alters the phase of radiation passing therethrough by a selected amount. The pixel arrangement is chosen, using computer modeling and optimization techniques, such that the interference pattern created by the collective pixels in a sub-element makes up the desired image (or a portion thereof). A technique is also provided for reducing the intensity of the image formed by a selected sub-element, which may be located in a laser "hot spot", by randomizing a selected percentage of the pixels located in that sub-element. This diffractive homogenizer is useful in various laser ablation and annealing and other laser material processing applications.
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Guenther Reid L.
Shoemaker Curtis L.
3M Innovative Properties Company
Assaf Fayez
Fonseca Darla P.
Spyrou Cassandra
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