Radial metrology combines standard optical measurement techniques with a unique panoramic annular lens (PAL) system to study material properties and deformations on the inner surfaces of the cavities found, for example, inside pipes, tubes, and boreholes. A PAL profilometer using speckle metrology is analyzed and the equations obtained from the analysis are used to calibrate the PAL profilometer when it is used to profile the inner surface of a cylindrical pipe and to measure the deformation of the pipe when it is subjected to diametral compression.
Donald R. Matthys,
John A. Gilbert,
"Endoscopic measurement using radial metrology with digital correlation," Optical Engineering 30(10), (1 October 1991). https://doi.org/10.1117/12.55965