Automatic plumb and level tool with acoustic measuring capability

Abstract

An automatic plumb, level, pointing and distance measuring tool uses a visible laser diode to project a beam in any of several different modes through a beam exit window. The tool, approximately the size and shape of a tape measure, can be placed on one edge to project a tilt-compensated vertical beam. Placed on another edge 90.degree.-rotated, the tool projects through the same exit window a tilt-compensated horizontal beam. When laid on either of its larger flat sides, the tilt compensation becomes inoperative and the tool projects a beam which is fixed relative to the housing. Acoustic distance measurement is facilitated using a second component or target side device which receives both a light beam an acoustic signal simultaneously projected from the laser tool across a space to be measured. A receiver in the target side device first detects arrival of a characteristically modulated or pulsed light beam, received at a photodetector on the target side device, and then receives the acoustic signal. A clock starts when the light beam is detected and stops when the acoustic signal is received. The acoustic transit time is thereby clocked and distance is calculated and displayed. The use of a single acoustic transit time, without reflection increases distance measuring range. Also, the visible laser beam projected between the two components provides a clear visual indication of the distance to be measured.