Holographic Device For Analysis Of Objects Inaccessible By Direct Microscopic Technique

In contrast with ordinary photographic techniques, a three dimensional analysis of transparent or opaque objects can be obtained by holographic technique, with combined properties which are not obtainable simultaneously by classical optics, namely: high resolution, wide field of view, large frontal distance. The last property is very useful in the case of difficult access to the object plane for any reason such as: cumbersome mechanics, safety considerations... A holographic device has been built for the investigation of the rectilinear discharge propagation on a surface intended to simulate, in the laboratory, the natural leader lightning phenomenon. The apparatus was designed in order to achieve both high temporal and spatial resolution, without neglecting the necessity of a minimum value of forty centimeters for the distance between the set-up and the electric phenomenon (120 kV). wo optical component is placed between the object plane and the hologram plate. ado, the resolution of the record only depends on the angle substending the holographic plate as measured from the object. A single exposure is used for the record of a hologram providing the shadowgraphy of the channel (optical phase object). The interferometric examination is also possible by means of the double exposure holographic method. With just a few minor modifications, the holographic set-up was also used for the study of the structure of a turbulent flame, for the high resolution record of opaqueobjects and the interferometric examination of their deformations. The reconstruction, from the holograhic plate, of a high resolution real image at the same size of the object is achieved by means of another especially designed set-up. this three dimensional image can be easily observed by means of a microscope, unlike the phenomenon itself which is brief and/or inaccessible. The two optical devices are described and various examples of applications are given.