The present invention relates to manipulation of coherent light beams and, more specifically, to methods and means for providing a coherent light beam which extends radially 360.degree. about a central axis perpendicular thereto.
Since their discovery and commercial introduction some 20 years ago, laser devices have been usefully employed in a wide number of applications. Among these are applications requiring that the beam axis be moved or scanned in a circular pattern about an axis perpendicular thereto. That is, the beam is caused to move through 360.degree. arcs about a central point on the plane. This is commonly accomplished by a mirror or prism placed on a direct or reflected beam axis and moved as required to effect the scan. Such devices are used, for example, in surveying and inspection applications, among others.
Such systems obviously require moving parts, e.g., a mirror or prism on the output shaft of a motor, and sometimes means such as a shaft encoder to generate clock signals which relate to the angular rotation of the mirror. In addition to increasing the costs of constructing and maintaining the apparatus, other problems are inherent in generating the desired beam scan, maintaining precise alignment of moving parts, and collecting the incident or reflected radiation, where required, for evaluation of various data produced thereby. The principal object of the present invention is to provide a method and apparatus for producing a beam in a circular pattern about an axis perpendicular to the beam with no moving parts.
A further object is to provide means for generating a beam of coherent light in a 360.degree. circular pattern which is of essentially constant intensity at each radial segment.
An additional object is to provide means for converting a relatively narrow, collimated beam of coherent radiation to an essentially planar beam extending infinitely outward for 360.degree. about a central point.
Still another object is to provide a method and means for pumping a resonant cavity to produce a laser beam extending for 360.degree. about a central point, either diverging from or converging to said point.
Other objects will in part be obvious and will in part appear hereinafter.