An asymmetry method for high precision alignment with laser light.

A new method of making precision alignment of rectilinear systems of any length without requiring high resolution optics is described. Laser light with antisymmetrical transverse phase is used to produce intensity asymmetries by means of diffraction behind a misaligned target. The apparatus is very simple but flexible enough to attain alignment of extreme accuracy within an operational range from zero to several kilometers. Under favorable conditions, misalignments of less than 0.01 mm are detectable (10(-8) rad at a distance of 1 km). Both visual and automated detection is possible in one as well as in two directions. The advantages of the asymmetry method are discussed with respect to conventional and existing laser techniques; applications and limitations are cited.