Calibration Issues with Shack-Hartman Sensors for Metrology Applications

John E. Greivenkamp, Daniel G. Smith, Eric Goodwin

Research output: Contribution to journalConference article

5 Scopus citations

Abstract

A long-standing goal of optical metrology is testing aspherics without the need for part-specific null lenses. The problem involves increasing the measurement dynamic range while preserving accuracy. The Shack-Hartmann wavefront sensor offers an interesting alternative to interferometry where the dynamic range is tied to the wavelength of light. Because the Shack-Hartmann wavefront sensor is a geometric test, the lenslet array can be designed in a way that trades sensitivity for dynamic range making it possible to test, without a null, aspheres that would otherwise require null optics. However, a system with this much dynamic range will have special calibration issues. Shack-Hartmann wavefront sensors are widely used in feedback control systems for adaptive optics. In that application, calibration is not a serious problem as the system drives the correction to a null; calibration errors slow the rate of convergence. For metrology applications, the calibration of the Shack-Hartmann wavefront sensor must be absolute. This presentation will discuss issues related to the design and calibration of a Shack-Hartmann metrology system including the design of an appropriate lenslet array, methods for dealing with induced aberrations, vignetting and spatial resolution limitations.

Original languageEnglish (US)
Pages (from-to)372-380
Number of pages9
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume5252
DOIs
StatePublished - May 3 2004
EventOptical Fabrication, Testing, and Metrology - St. Etienne, France
Duration: Sep 30 2003Oct 3 2003

Keywords

  • Aspheres
  • Optical Testing
  • Shack-Hartmann
  • Wavefront Sensors

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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