title: Continuous-wave ultrasound reflectometry for surface roughness imaging applications.
abstract: BACKGROUND
  Measurement of surface roughness irregularities that result from various sources such as manufacturing processes, surface damage, and corrosion, is an important indicator of product quality for many nondestructive testing (NDT) industries. Many techniques exist, however because of their qualitative, time-consuming and direct-contact modes, it is of some importance to work out new experimental methods and efficient tools for quantitative estimation of surface roughness.
  
  
  OBJECTIVE
  Here we present continuous-wave ultrasound reflectometry (CWUR) as a novel nondestructive modality for imaging and measuring surface roughness in a non-contact mode. In CWUR, voltage variations due to phase shifts in the reflected ultrasound waves are recorded and processed to form an image of surface roughness.
  
  
  RESULTS
  An acrylic test block with surface irregularities ranging from 4.22 microm to 19.05 microm as measured by a coordinate measuring machine (CMM), is scanned by an ultrasound transducer having a diameter of 45 mm, a focal distance of 70 mm, and a central frequency of 3 MHz. It is shown that CWUR technique gives very good agreement with the results obtained through CMM inasmuch as the maximum average percent error is around 11.5%.
  
  
  CONCLUSIONS
  Images obtained here demonstrate that CWUR may be used as a powerful non-contact and quantitative tool for nondestructive inspection and imaging of surface irregularities at the micron-size level with an average error of less than 11.5%.
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine, Ultrasound Research Laboratory, Rochester, MN 55905, United States. mitri@ieee.org
authors.forename: F G
authors.initials: FG
authors.lastname: Mitri
authors.forename: R R
authors.initials: RR
authors.lastname: Kinnick
authors.forename: J F
authors.initials: JF
authors.lastname: Greenleaf
authors.forename: M
authors.initials: M
authors.lastname: Fatemi
mesh_terms: D000465:Algorithms; D008422:Materials Testing / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D012542:Scattering, Radiation; D013499:Surface Properties; D014463:Ultrasonography / Q000379:methods*