4. Static tomographic lighting

Static sheets are obtained by spreading a laser beam using spherical-cylindrical optical components; the basic set-ups comprise just two lenses and offer the advantage of easy adjustment, even for operators unfamiliar with optics: on the other hand, the geometry of the sheets thus obtained is fixed by the choice of focal lengths. Fixtures that allow divergence and working distance to be varied require at least 3 or 4 components to be aligned.

• Divergent sheets: focusing-spreading assemblies

  A lens with a long focal length or a telescope focuses the beam in the study zone. A cylindrical lens performs the spreading function in a single direction, imposing the divergence and extent of the sheet (figures 4 a,