PROCEDURE FOR THE USE OF INTERFEROMETRIC INFORMATION FROM TWO DIFFERENT HOLOGRAMS EXPOSED IN A SHORT-TERM RELATIONSHIP

摘要

The present invention is directed to a holographic interferometer for measuring the deformation of an object or mechanical structure by exposing one or more hologram plates to a light source and a reference beam. In particular, the invention is directed to a method and apparatus for moving the hologram plate during and between exposures to thereby obtain exposures on different portions of the hologram plate. Each of these different exposures is taken in a short time interval in response to light reflected by the object from the light source as well as light from the reference beam. The image on the hologram plates is then reconstructed in a manner generally known in the art to determine the deformation of the object or mechanical structure. In order to obtain these exposures on different portions of the hologram plates, a screen having one or more apertures is positioned in front of the hologram plates to restrict the size of the short time interval exposures on the hologram plates. The hologram plates are continuously rotated prior to and during the exposures about an axis of rotation which is located perpendicularly to the surface of the hologram plates and is positioned so that some portion of the hologram plates is always located behind the aperture in the screen. In order to obtain a suitable direction of the interference lines, the reference beam, the aperture in the screen, the object and the axis of rotation of the hologram plates are positioned in the same plane. In the preferred embodiment, two different hologram plates are rotated together behind the screen. During reconstruction, these different hologram plates are positioned adjacent one another so that the surfaces of the forward hologram plate exposed by the first exposure pulse cover the surfaces of the rearward hologram plate exposed by the second exposure pulse, or vice versa. As a result, the interference lines in the hologram image correspond to the object or mechanical structure which is being measured for deformation.