Abstract: Alignment marks in the form of periodic gratings are scanned by a TV camera, and the relative phase difference of the two scanning signals is electronically determined by digital or analog means. In the former case, a microprocessor computes at least the fundamental wave of the Fourier spectrum of each scanning signal, in order to compute relative alignment from the phase positions of the fundamental waves. If gratings with different grating periods are used on the objects to be mutually aligned, the superimposition of the computed fundamental waves leads to the generation of beats which constitute a highly sensitive measure of alignment errors. For an alternative analog evaluation, one of the scanning signals is delayed to compensate for the difference in scan timing before being fed with the other signal to a phase-sensitive amplifier for determining the phase difference.

Abstract: For the point-by-point interferometric measuring of surfaces which are scanned along lines, or which are subjected to a processing procedure (e.g. etching) a focused laser beam is directed with oblique incidence as a measuring beam onto the respective measured points. The respective height of a measured point determines the path difference (phase difference) between the measuring beam and a reference beam which has been suitably split off the input beam. The oblique incidence (angle of incidence .gtorsim.80.degree.) makes it possible to measure interferometrically very rough surfaces. The measuring range may be extended if the reference beam is directed at an oblique angle of incidence, differing only slightly from that of the measuring beam onto the surface to be examined.

Abstract: A radiation analyzing system including a beam splitting prism, an analyzer and a photodiode array arranged in an evaluation plane. Upon passing through the prism radiation to be analyzed is split into two beams vertically linearly polarized to each other which include a small angle and show a phase shift that is a function of the distance from the optical axis. The difference of the phase positions of these two beams is a function of their distance from the left or right edge of the prism. The analyzer, which is arranged behind the prism and whose axis of polarization is inclined relative to the directions of polarization of the two vertically polarized beams, produces a periodic intensity distribution when the impinging radiation is polarized at least partly and has a component in parallel to the axis of the analyzer.

Abstract: 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.