Abstract: The optical properties of circular prisms, which are also known as axicons, are utilized in optical systems that generate one or more quiescent, steady in time, sharply focused circular and arc-shaped patterns of light. A laser beam incident on the circular prism is deviated by the prism effect and the emerging beam focused onto a target surface by a spherical lens or zoom lens; the radius of the circle is conveniently adjusted. Systems with stationary optics are described to efficiently form two concentric, uniform circles, or two offset circular or approximately circular arcs, from input beams derived from one or two lasers. These structured light patterns are used in tracking an edge or groove, for instance to locate the workpiece joint in robotic arc welding.

Abstract: Optical triangulation is used for determining the profile of a surface with only two photomultiplier tubes needed for optical sensing in a flying spot camera system. A feedback arrangement varies the angle at which a laser beam is applied to the surface such that the image of the beam on the surface tends to be maintained constant with respect to a linear reference position parallel to a scanning direction. Deviations in the image from its reference position as caused by surface height variations are used in the feedback arrangement to change the deflection angle. The deflection angle is in turn detected and is indicative of the variations in surface height. As an anti-noise feature, amplitude modulation is impressed upon the laser beam directed towards the surface and a filter network is used to filter photomultiplier response so as to exclude response to background optical noise.

Abstract: In an arc welding operation seam tracking is accomplished by determining the level of infrared radiation in a selected bandwidth, from at least two points lying in a direction forward of the arc torch travel and on opposite sides of the seam. Signal levels from the infrared detectors are compared and the difference signal is used to laterally position the arc torch. In this way, automatic seam tracking is accomplished thus facilitating robotic welding processes.

Abstract: An instrument to make simultaneous accurate measurements of the intensity of light in each of two (or more) spectral channels using a single interference filter employs mirrors or prisms to break up the observed light beam into two (or more) beams, propagating in slightly different directions. The angle dependence of the filter spectral passband provides two distinct spectral channels which are focused onto separate detector elements. Advantages of this instrument are illustrated by its application for remote point Raman temperature measurements in hot gases.

Abstract: An object is tested for thickness or for presence and location of flaws by impacting a pulsed laser beam on the surface of the object so as to generate ultrasonic waves by rapid heating of a thin surface layer thereon. The reflected ultrasonic echo in the object is detected by monitoring surface motion with a rough surface interferometer.