Abstract: A system for monitoring changes in shape of a structure employs a laser source attached to the structure and a set of beam splitters mounted at various locations on the structure and arranged to route portions of a laser beam produced by the laser source into various video cameras also mounted on the structure. Each video camera includes a photodetector array and produces an output signal indicating the intensity of light detected by each photodetector of the array, thereby indicating the beam intensity distribution in a corresponding plane of interest. The video output signal of each camera is digitized and stored as an intensity data array in the memory of a digital computer. The computer calculates from the intensity data array the position of the centroid of the beam with respect to a reference point on the plane of interest using a least squares fit of the intensity data to a two-dimensional Gaussian intensity distribution.

Abstract: A device is shown for use in a dental office or the like where particles of precious metal or amalgam are to be recovered from a flushing stream. The construction utilizes a housing for enclosing a downwardly sloping trough element through which a flushing liquid flows so that the particles of metal or amalgam can deposit in compartments formed in the trough while the flushing liquid and any residual debris which floats in the liquid flows through an outlet to a sewage disposal means.