le, the wave fronts of the reflected beam will be spherical; the interference pattern produced on the film will then consist of concentric circles, the space between circles decreasing with increasing radius.The interference pattern produced by a more complicated object will be much more complicated, so mere inspection of the resulting hologram will reveal only an intricate pattern of dark and light structures that bear no apparent relationship to the original object. When the hologram is viewed in coherent light, however, the recorded object becomes visible; and when the hologram is viewed from different angles, the object is also seen from different angles. The three-dimensional effect is obtained because the hologram reconstructs in space the wave fronts that originally were produced by the object.How this happens can be understood by again using the example of the hologram of the point. Coherent light arriving at the concentric circles on the hologram is diffracted on a diffraction grating. The diffraction angle of the beam increases with the distance from the center of the concentric rings, thus reconstructing the spherical wave fronts, and the viewer sees the point at the same relative place where the real point was when the hologram was made. The wave fronts of more complicated objects are reconstructed in the same way. The intensity distribution of the reflected light is recorded in the degree of blackening of the interference patterns on the film.Applications,To a certain extent, holography can be applied in optical microscopy, especially for the study of living organisms. The most successful application of holography, however, is in interferometry. If two holograms of the same object are recorded on the same plate, then upon reconstruction the two holographic images will interfere. If the object has undergone a deformation between the two recordings, phase differences in certain parts of the two images will result, creating an...
