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Papers by Danette Fitzgerald

Proceedings of SPIE, Jun 26, 2017

Calibration, adjustment and verification of surface topography measuring instruments are importan... more Calibration, adjustment and verification of surface topography measuring instruments are important tasks, often facilitated by precision step-height specimens that have been calibrated using traceable metrology such as interferometry. Although standardized procedures for calculating parameters of the step-height are available for line profiling contact stylus systems, there is inconsistent guidance as to how to interpret step height data for 3D, areal surface topography instruments, such as confocal and interference microscopes. Here we provide definitions for the reference and measurement areas of step-height specimens as well as practical measurement protocols for processing the surface topography map.

An important characterization for surface topography instruments is a traceable calibration of th... more An important characterization for surface topography instruments is a traceable calibration of the height scale. We calibrate our coherence scanning interference microscopes using a natural spectral emission line in place of a sequence of material measures such as step-height specimens. The uncertainty budget for our approach includes estimates for several error sources associated with long term drift. Here we summarize results collected over 3 years’ experience from our laboratories to provide statistical support for confirming and refining these uncertainty contributions. We find that the source wavelength stability is < 0.005% RMS and the stability of the height scaling factor (the amplification coefficient) is < 0.02% RMS over 900 days. Both values are better than our original estimates. We also show < 0.13% RMS reproducibility of the complete traceable process using acceptance test data for over 100 manufactured instruments. Finally, we report results of 3 years of experience in certifying step-height specimens using the traceable wavelength method.

Applied Optical Metrology III, 2019

Optical Measurement Systems for Industrial Inspection X, 2017

Cryogenic Optical Systems and Instruments X, 2003

The Infrared Multi-Object Spectrometer (IRA408 is a principle investigator class instrument for t... more The Infrared Multi-Object Spectrometer (IRA408 is a principle investigator class instrument for the Kitt Peak National Observatory 4 and 2.1 m telescopes. IRA4OS is a near-IR (0.8-2.5 pm) spectrometer with low-to mid-resolving power (R = 300-3000). IRA4OS produces simultaneous spectra of-100 objects in its 2.8 x 2.0 arc-min field of view (4 m telescope) using a commercial Micro Electro-Mechanical Systems (MEMS) micro-mirror array (MMA) from Texas Instruments. The I W O S optical design consists of two imaging subsystems. The focal reducer images the focal plane of the telescope onto the MMA field stop, and the spectrograph images the MMA onto the detector. We describe ambient breadboard subsystem alignment and imaging pe~%ormance of each stage independently, and ambient imaging performance of the fully assembled instrument-Lnterferometric measurements of subsystem wavefront error serve as a qualitative alignment guide, and are accomplished using a commercial, modified Twyman-Green laser unequal path interferometer. Image testing provides verification of the optomechanical alignment method and a measurement of nearangle scattered light due to mirror small-scale surface error. Image testing is performed at multiple field points. A mercury-argon pencil lamp provides a spectral line at 546.1 nm, a blackbody source provides a line at 1550 nm, and a CCD camera and IR camera are used as detectors. We use commercial optical modeling sofiware to predict the pointspread function and its effect on inshument slit transmission and resolution. Our breadboard and instrument level test results validate this prediction. We conclude with an instrument performance prediction for cryogenic operation and first light in late 2003.

Ground-based Instrumentation for Astronomy, 2004

The Infrared Multi-Object Spectrometer (IRMOS) is a principle investigator-class instrument for t... more The Infrared Multi-Object Spectrometer (IRMOS) is a principle investigator-class instrument for the Kitt Peak National Observatory 2.1 m and Mayall 3.8 m telescopes. IRMOS is a near-IR (0.8--2.5 micron) spectrometer with low- to mid-resolving power (R = lambda/Deltalambda = 300-3000). On the 3.8 m telescope, IRMOS produces simultaneous spectra of ~100 objects in its 2.8 ' 2.0 arcmin field of view using a commercial micro electro-mechanical systems (MEMS) digital micro-mirror device (DMD) from Texas Instruments. The multi-mirror array DMD operates as a real-time programmable slit mask. The all-reflective optical design consists of two imaging subsystems. The focal reducer images the focal plane of the telescope onto the DMD field stop, and the spectrograph images the DMD onto a large-format detector. The instrument operates at ~90 K, cooled by a single electro-mechanical cryocooler. The bench and all components are made from aluminum 6061. There are three cryogenic mechanisms. We describe laboratory integration and test of IRMOS before shipment to Kitt Peak National Observatory. We give an overview of the optical alignment technique and integration of optical, mechanical, electrical and cryogenic subsystems. We compare optical test results to model predictions of point spread function size. We discuss some lessons learned and conclude with a prediction for performance on the telescope.