Pulsed sandwich holography. 2: Practical application

The vibration of a small electric drilling machine was studied holographically. The machine was held by hand, and drilling was done on a steel plate during two exposures from a double pulsed ruby laser. The recording was made on a rotating sandwich hologram. The influence of rigid motion was eliminated, and the local vibration evaluated. The phase relation between different areas was studied using three methods, all based on the simple idea that interference fringes are formed when a modified object surface is intersected by interference planes which tilt in the same direction as the observer tilts the sandwich hologram during the reconstruction.