Pinhole method, cameras

The pinhole method is used in studies of preferred orientation, grain size, and crystal quality. With a back-reflection camera, fairly precise parameter measurements can be made by this method. Precise knowledge of the specimen-to-film distance D is not necessary, provided the proper extrapolation equation is used (Chap. 11) or the camera is calibrated. The calibration is usually performed for each exposure, simply by smearing a thin layer of the calibrating powder over the surface of the specimen in this way, reference lines of known 0 value are formed on each film. 

Fio. 165. The fly s eye method, a. Part of multiple pinhole camera. 6. Arrangement for making repeating patterns by the multiple pinhole camera. Atoms in the unit cell are represented by points of light. 

When monochromatic radiation is used to examine a powder specimen in a Laue (flat-film) camera, the result is often called, for no particularly good reason, a pinhole photograph. (There is no general agreement on the name of this method. Klug and Alexander [G.39], for example, call it the monochromatic-pinhole technique. ) Either a transmission or a back-reflection camera may be used. A typical transmission photograph, made of fine-grained aluminum sheet, is shown in Fig. 6-11. 

The interference filter method was also used by Ruf and Winkler [239] for the detection of oil backstreaming in oil diffusion pumps with a pinhole-camera arrangement. 

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