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Ab Id-Kort

Nils Abramson

Hans Bjelkhagen

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.

Method of utilizing interferometric information from two different

A method for establishing and reading secret information using holographic interference pattern techniques. A holographic plate is placed in a holder and exposed with a laser light reflected from an object and a reference laser light to create a hologram. The exposed hologram is removed and a second holographic plate is inserted into the holder. The object, which may be a matrix, is selectively deformed to provide letters or numbers in accordance with the secret information to be established. The second holographic plate is then exposed with a light reflected from the deformed object and with the reference laser light to create a second hologram. The information contained on each hologram, when viewed individually, appears to be substantially identical. However, when the two holograms are later combined and illuminated, the secret information in the form of a holographic interference pattern will be observed in the hologram.

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Stockholm, Sweden

Nils Abramson