| Popis: |
For many years opticists have been contouring optical surfaces for deformations of the order of a few microns by the use of interferometric techniques. One of the earliest methods for doing this is to place a reference surface over the surface to be contoured. When this combination is illuminated by a coherent colli-mated beam, a fringe pattern is observed that is localized close to the surface that is being contoured. The fringe pattern (interferogram) is easily interpreted to yield contour information. This simple device (interferometer) is known as a Fizeau interferometer. (Ref. 1) As can be easily seen this experiment (and other interferometric techniques) is only applicable to surfaces which are smooth compared to the wavelength of the light used. The object must also have deformations from the reference surface not much larger than a few wavelengths of the light. In an effort to contour rougher surfaces and greater deformations than are allowed by using visible light, longer wavelength light such as the radiation from a CO2 laser is used. Unfortunately there exist many objects that are too rough and have too great a deformation to be suitable for an interferometer even with these longer wavelengths. At present, many of the objects of this type are handled by the conventional techniques of close-range photogrammetry (Ref. 2) and moire fringes. (Ref. 3)© (1974) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
