Calibration issues with Shack-Hartmann sensors for metrology applications

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

doi:10.1117/12.513462

26 February 2004 Calibration issues with Shack-Hartmann sensors for metrology applications

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

Proceedings Volume 5252, Optical Fabrication, Testing, and Metrology; (2004) https://doi.org/10.1117/12.513462
Event: Optical Systems Design, 2003, St. Etienne, France

Abstract

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.

Citation Download Citation

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); https://doi.org/10.1117/12.513462

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