Workpiece heat expansion measurement - using laser beam interferometry to measure test piece dependent path length change

摘要

The test piece is mounted in a groove in a mounting block and quartz crystals having a reflective surface are placed at each end of the test piece. Two laser beams are then directed along the groove at the test piece and the crystals, and, if the test piece is transparent, one beam is reflected by the crystal, at the far end of the test piece, through it, and the other by the crystal at the near end. The two reflected beams are directed via a mirror to an interferometer, when the pattern is used to detect and measure any test piece expansion. If the test piece is not of transparent material, an axial hole may be drilled through it to allow the necessary passage of the laser beam.