Use of Fresnel zone plates for material processing

Details Use of Fresnel zone plates for material processing Use of Fresnel zone plates for material processing

1992-09-03

1994-11-08

Albritton, C. L.

Electric heating

Metal heating

By arc

21912173, 21912176, 21912183, B23K 2600

Patent

active

053629400

ABSTRACT:
The apparatus for machining and material processing includes an excimer laser and a Fresnel zone plate array (FZP) positioned parallel to the workpiece, with the distance between the FZP and the workpiece being the focal length of the FZP. For each hole to be formed on the workpiece a corresponding Fresnel zone is patterned onto the FZP. Each Fresnel zone may be patterned directly centered over the desired hole location or in high density patterns it may be located off-center from the hole with deflection being accomplished by the formation of finer circular arcs on the side of the Fresnel zone opposite the desired direction of deflection. A beam scanner is included to provide a more uniform illumination of the FZP by the laser beam. The scanning eliminates non-uniformity of intensity. The alignment mechanism uses a helium-neon laser, the beam from which is projected onto a surface relief grating on the workpiece. The reflected light from the surface relief grating is filtered to create interference fringes which, when aligned, provide maximum light intensity projected through a transmission grating on the Fresnel zone plate.

REFERENCES:
patent: 4909818 (1990-03-01), Jones
Engel, et al., "Laser Machining with Modulated Zone Plates", Applied Optic Feb. 1974, vol. 13, No. 2, pp. 169-273.
Moran, et al., "Laser Machining with a Holographic Lens", Applied Optic Feb. 1971, vol. 10, No. 2, pp. 412-415.
Campbell, et al., "Materials processing with CO.sub.2 laser holographic scanner systems", Applied Optics, 1 Dec. 1978, vol. 17, No. 23, pp. 3727-3737.
Gallagher, et al., "Infrared Holographic Optical Elements with Applications to Laser Material Processing", IEEE Journal of Quantum Electronics, vol. QE-15, No. 12, Dec. 1979, pp. 1369-1381.

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