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26 February 2004 Calibration issues with Shack-Hartmann sensors for metrology applications
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A long-standing goal of optical metrology is testing aspherics without the need for part specific nulls 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.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John E. Greivenkamp, Daniel G. Smith, and Eric Goodwin "Calibration issues with Shack-Hartmann sensors for metrology applications", Proc. SPIE 5252, Optical Fabrication, Testing, and Metrology, (26 February 2004);


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