Abstract: An optical head for a shearography system includes any standard TV camera lens 56, such as a wide-angle lens, which views a region of a test object 50 that is illuminated by coherent light 52. The lens 56 creates an image at an image plane where a field lens 80 is located. The field lens 80 redirects the light so as to allow substantially all the light of the image to pass through a first relay lens 86, thereby projecting the image with uniform brightness, i.e, no vignetting. The lens 86 provides collimated light 88,90 to a shearing element, such as a Michelson interferometer, comprising a beamsplitter 92 and two mirrors 94,96. Use of collimated light minimizes aberrations typically caused by beamsplitters. Collimated output light 102,104 from the shearing element is refocused onto a TV camera sensor plate 112 where the sheared interfered image is electronically detected for processing and viewing.

Abstract: An airflow detection system comprising a light source for generating an optical signal that is propagated in an optical guide having a plurality of sensors responsive to the presence of airflow, each of which modulates the intensity of the optical signal at a frequency characteristic of that sensor such that a detection apparatus can receive the optical signal and identify activated sensors using frequency domain multiplexing techniques.

Abstract: A noncontact optical strain gauge may be used for high temperature objects and objects having a small radius of curvature in the area of interest. The gauge works by means of interferometry applied to the speckle patterns of radiation reflected from two points on the object surface.

Abstract: A mechanical scanning apparatus adapted for oscillating the focus zone of a beam of radiation having high power to modify and control the nature and extent of the interaction zone on a workpiece is disclosed. The apparatus includes a compound beam adapted for being vibrated in a vibratory mode resulting in oscillatory motion of at least a first end of the compound beam; a reflective surface attached to the first end of the compound beam and adapted for focussing radiation incident thereon to a focus zone, and means for vibrating the compound beam to induce oscillatory motion of the reflective surface resulting in oscillatory motion of the focus zone. For vibration frequencies greater than the characteristic thermal response time of the workpiece material, the effect is a broadening of the interaction zone with a beam-material interaction characteristic of a reduced incident average power intensity while maintaining a high local intensity essential to the establishment of effective radiation-material coupling.

Abstract: A mechanical scanning apparatus adapted for oscillating the focus zone of a beam of radiation having high power to modify and control the nature and extent of the interaction zone on a workpiece is disclosed. The apparatus includes a compound beam adapted for being vibrated in a vibratory mode resulting in oscillatory motion of at least a first end of the compound beam; a reflective surface attached to the first end of the compound beam and adapted for focussing radiation incident thereon to a focus zone, and means for vibrating the compound beam to induce oscillatory motion of the reflective surface resulting in oscillatory motion of the focus zone. For vibration frequencies greater than the characteristic thermal response time of the workpiece material, the effect is a broadening of the interaction zone with a beam-material interaction characteristic of a reduced incident average power intensity while maintaining a high local intensity essential to the establishment of effective radiation-material coupling.

Abstract: A violin, as representative of any of the members of the viol and violin families, has a soundbox with an improved back plate construction. The back plate is substantially flat and has affixed to it braces for resonance balancing with the top plate. The braces include an elongate, primary brace disposed parallel to the longitudinal axis of the back plate, and first and second sets of secondary braces which are longitudinally spaced from each other. Each set of secondary braces comprises a pair of short, brace segments which are laterally disposed on the other side of the primary brace and in oppositely registering positions with respect thereto.