International Business Machines Corporation

Arno Schmackpfeffer

Gunter Makosch

Walter Jaerisch

Guenter Makosch

Franz J Schedewie

Jorg Ziller

The gaussian energy distribution common to all laser beams is a serious handicap in most laser beam applications for machining material, such as for drilling, welding and the like. This is especially true in welding extremely thin metal sheets, as in the manufacture and assembly of the transducers of modern magnetic disk files. According to the subject invention, a laser beam is directed to a glass cone or axicon which converts the gaussian energy distribution of the laser beam to one more uniform in cross-section. Depending on the distance of the workpiece from the exit side of the axicon, the energy distribution of the radiation impinging onto the workpiece will be either uniform, saddle shaped or annular cross-section. It has been discovered that saddle shaped or annular energy distributions are optimal for welding very thin metal sheets by a laser beam since the heat dissipation in the center of a welding spot is a minimum and that at the periphery of the laser beam depends on the material, size and shape of the workpiece, which parameters can be matched by adjusting the distance between the axicon and the workpiece.

Apparatus for machining material

Disclosed is an interferometric apparatus and method for the inspection and detection of overlay errors characterized in that two plane polarized laser beams are directed onto the surface to be inspected, the angle included by these two beams being dimensioned in such a way that the radiation generating the plus or minus first order of the diffraction pattern of one beam is parallel to the other beam, thus generating an interference field which in the absence of overlay errors consists of an homogeneous fringe pattern while in the presence of such errors the fringe pattern is locally distorted. In a first embodiment, a first component of a laser beam is deflected onto a viewing screen by a beam splitter while a second component passes through the beam splitter to a mirror. The position and angle of the mirror is determined by the first order diffraction characteristics of the grating (object). The second component provides a first order of diffraction which interferes with the first component, producing an interference pattern on the viewing screen.

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Boeblingen, Germany

Arno Schmackpfeffer