CHOPPER DEVICE FOR LASER HOLOGRAPHIC INTERFEROMETER

摘要

PURPOSE:To detect the vibration node of an object, by forming radial slits in a slit disk which intermittently cuts a laser beam, providing the slit intervals having unequal pitches, thereby detecting the deviation of interference fringes. CONSTITUTION:With the output of an oscillating part 2 as a reference signal, a motor 7 is controlled, and the slit disk 6, which intermittently cuts the laser beam 5, is driven. A vibrating machine 9 is controlled at the same time, and the object to be measured 8 is vibrated. The light A from the object and reference light B are introduced to a dry plate 12. Then the deformation and a vibrating figure of the object 8 are measured based on the brightness of the interference fringes. In this case, the slits provided in the slit disk 6 are formed so that interval l in the first half circumference of the disk 6 is made all equal, and the intervals in the last half circumference are shifted by an infinitesimal interval epsilon with respect to the first half circumference. Therefore the part, where the interval between the fringe lines becomes narrow, represents the node part of the vibrating figure, and the vibrating node of the object can be readily found.