Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Perspective View of the Knife-edge Pinhole Collimator. A point source at z = h and angle θ emits a photon that intersects the z = 0 plane at (ρ cos β, ρ sin β, 0) with an incident angle θa. The acceptance angle of the collimator is α and the diameter of the aperture is d. ΔL is the path length of the photon in the attenuating medium. Reproduced from [6] with permission (© 2001 IEEE).
