Visual Scanning Hartmann Optical Tester (VSHOT) Uncertainty Analysis (Milestone Report)

Research output: NRELTechnical Report


In 1997, an uncertainty analysis was conducted of the Video Scanning Hartmann Optical Tester (VSHOT). In 2010, we have completed a new analysis, based primarily on the geometric optics of the system, and it shows sensitivities to various design and operational parameters. We discuss sources of error with measuring devices, instrument calibrations, and operator measurements for a parabolic troughmirror panel test. These help to guide the operator in proper setup, and help end-users to understand the data they are provided. We include both the systematic (bias) and random (precision) errors for VSHOT testing and their contributions to the uncertainty. The contributing factors we considered in this study are: target tilt; target face to laser output distance; instrument vertical offset;laser output angle; distance between the tool and the test piece; camera calibration; and laser scanner. These contributing factors were applied to the calculated slope error, focal length, and test article tilt that are generated by the VSHOT data processing. Results show the estimated 2-sigma uncertainty in slope error for a parabolic trough line scan test to be +/-0.2 milliradians;uncertainty in the focal length is +/- 0.1 mm, and the uncertainty in test article tilt is +/- 0.04 milliradians.
Original languageAmerican English
Number of pages41
StatePublished - 2010

NREL Publication Number

  • NREL/TP-5500-48482


  • CSP
  • parabolic trough
  • random error
  • sensitivity
  • systematic error
  • uncertainty analysis
  • Video Scanning Hartmann Optical Tester (VSHOT)


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