What does a pyramidal beam result in?

• A. Cylindrical field of view
• B. Spherical field of view
• C. Elliptical field of view
• D. Cubical field of view

Answer: (A)

Beam shape directly controls how the illuminated area expands as the beam travels. A pyramidal beam expands uniformly around its central axis, so at any fixed distance from the source the cross-section of the illuminated region is circular. That circular cross-section along the depth direction forms a cylindrical footprint on the target or detector, giving a cylindrical field of view.

If a field of view were spherical, the expansion would have to come from a single point radiating in all directions, which isn’t the characteristic of a pyramidal beam. An elliptical field of view would require anisotropic (unequal) spreading in two orthogonal directions, and a cubical field of view doesn’t arise from smooth, axisymmetric beam expansion.