Peter J. DE GROOT

Peter J. DE GROOT
Zygo Corporation · Executive staff

PhD

About

370
Publications
124,876
Reads
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5,039
Citations
Introduction
Peter invents and develops new optical metrology instruments for Zygo Corporation in Middlefield, Connecticut. He is a Fellow of the SPIE, Optica, the Institute of Physics, and the International Academy of Engineering Technology, and is the 2023 Vice President Elect for SPIE. A multiple award winner for innovation, Peter is also a conference organizer, a scientific committee member, and an active contributor in the optics community.
Additional affiliations
July 2017 - present
University of Nottingham
Position
  • Professor
August 2015 - December 2015
University of Hartford
Position
  • Professor (Associate)
Description
  • Teach graduate courses in Optical Metrology
September 1992 - July 2021
Zygo Corporation
Position
  • Managing Director
Education
January 1985 - May 1987
University of Connecticut
Field of study
  • Physics
September 1983 - December 1984
University of Maine
Field of study
  • Physics
August 1982 - May 1983

Publications

Publications (370)
Chapter
Full-text available
The wavelength of light provides an exceedingly precise measure of distance and is the foundation for commercial interferometric measurement tools that monitor object positions with a resolution better than 1 nm for objects traveling at 2 m/s. A wide range of applications include machine tool stage positioning and distance monitoring over length sc...
Article
Full-text available
Interference microscopy plays a central role in noncontact strategies for process development and quality control, providing full 3D measurement of surface characteristics that influence the functional behavior of manufactured parts. Here I briefly review the history and principles of this important technique, then concentrate on the details of har...
Conference Paper
Full-text available
The demands of modern precision engineering exemplified by semiconductor photolithography systems have propelled encoder technology to a performance level surpassing that of line-of-site interferometry. The key advantage in these systems is the nearly complete suppression of air turbulence. This advance has come at the price of increased demands on...
Article
Full-text available
For optical measurements of areal surface topography, the instrument transfer function (ITF) quantifies height response as a function of the lateral spatial frequency content of the surface. The ITF is used widely for optical full-field instruments such as Fizeau interferometers, confocal microscopes, interference microscopes, and fringe projection...
Article
Full-text available
We propose an model for coherence scanning interferometry using familiar Fourier optics methods and the spectrum of plane waves for the case where light source spectral bandwidth limits the fringe contrast as a function of optical path length. The model is straightforward to implement, is computationally efficient, and reveals many of the common er...
Presentation
Optical surface topography measurement is a key component of optical fabrication as well as for precision manufacturing of products that range from additively-manufactured parts to immersive displays for augmented reality. Dominant measurement techniques today involve measuring microscopes, confocal and focus-variation microscopy, triangulation and...
Article
Full-text available
Metrology tools for immersive reality devices offer assistance in development and prototyping, performance evaluation, and production quality control. View online here: www.laserfocusworld.com/test-measurement/article/14277747/metrology-meets-the-challenges-of-immersive-reality-technologies
Conference Paper
Full-text available
A metrological characteristic common to all methods for areal surface topography measurement is the topographic spatial resolution (TSR), defined as the ability to distinguish closely-spaced surface features. This ability is limited in mechanical stylus instruments by the stylus tip geometry, while for instruments that rely on optical imaging, infl...
Conference Paper
Full-text available
Freeform optical surface shapes have evolved from an intriguing optical design concept to a practical necessity for applications ranging from space and defense to consumer electronics. The demand for freeform solutions is no more strongly felt than in the development of digital immersive displays for augmented and mixed reality, where the combinati...
Presentation
Full-text available
You can view the live presentation here: https://www.youtube.com/watch?v=owoI99sKn2k
Article
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An international comparison of surface topography flatness deviation was carried out. The comparison involved twelve optical surface topography instruments (focus variation instruments, confocal microscopes and coherence scanning interferometers) from six European research laboratories. The results demonstrated the following: (i) The flatness varie...
Presentation
Full-text available
When looking at the role of metrology in the ‘Fourth Industrial Revolution,’ one wonders whether metrology developments are being driven by Industry 4.0, or the other way around. Closed-loop manufacturing quality control is, after all, the art of the possible. For optical dimensional metrology and surface topography, advances in the ‘Internet of Th...
Article
Full-text available
Did Denis Gabor build the first all-optical computer for processing interference fringe patterns? Was Isaac Newton the first to create a synthetic off-axis hologram? Is my white-light 3D profiler actually a digital holography system? These are some of the questions addressed in this paper, which considers the many contributions of holography to the...
Conference Paper
Holography was invented 75 years ago by Dennis Gabor. Meanwhile it is much more than a fascinating technique for the recording and reconstruction of 3D images. The paper addresses the outstanding peculiarities and the big variety of applications of holography.
Article
Full-text available
The capability of optical surface topography measurement methods for measurement of steep and tilted surfaces is investigated through modelling of a coherence scanning interferometer. Of particular interest is the effect on the interference signal and measured topography when tilting the object at angles larger than the numerical aperture slope lim...
Conference Paper
Full-text available
We propose an instrument model for coherence scanning interferometry using familiar Fourier optics methods, the spectrum of plane waves, and the assumption that the light source spectral bandwidth is the dominant factor in determining fringe contrast as a function of optical path length. The model is straightforward to implement, is computationally...
Conference Paper
Full-text available
A powerful technique for interference fringe analysis uses tunable light sources. Originally developed to solve the problem of phase shifting in large aperture systems, the technique has evolved to the simultaneous measurement of multiple surfaces and optical thickness of optical assemblies and components. Here we review the principles and current...
Article
Full-text available
When looking at the place of metrology in the ‘fourth industrial revolution', it is interesting to ponder whether industry 4.0 is being driven by developments in metrology or metrology developments are being driven by Industry 4.0.
Presentation
Full-text available
https://www.youtube.com/watch?v=WNaX0rXfyUs: Optical instruments have long played a role in manufacturing, and strong arguments favor accelerated adoption of fast, non-contact measurements of surfaces, shapes and positions as an enabler for industry 4.0. High-precision techniques such as optical interferometry have advanced considerably and have...
Article
Full-text available
An international comparison of surface topography measurement noise was carried out. The comparison involved twelve optical surface topography instruments(focus variation instruments, confocal microscopes and coherence scanning interferometers)from six European research laboratories. The purpose of this comparison was to perform a practical test of...
Presentation
A brief (22 minutes) informal lecture on the physical modeling of interferometers. https://www.youtube.com/watch?v=WCPQLZrZfZM
Presentation
Presentation link: https://www.mcddm.ac.uk/events/christmas-lecture-2020.aspx This is a presentation of the inaugural lecture of the Midlands Centre for Data-Driven Metrology lecture series. This "Christmas Lecture" was attended by industry and research partners from across the globe. Abstract: Optical instruments have long played a role in man...
Presentation
Full-text available
Tutorial on the fundamentals of optics in the context of optical dimensional metrology for precision engineering applications. Presented as professional short course spanning two half days.
Conference Paper
Full-text available
Interferometers for the measurement of topography rely on imaging systems to map surface points to a camera. The response of an interferometer to variations in surface height depends on the filtering properties of the imaging system. Here we provide a simple and practical model of an imaging interferometer using classical Fourier optics, including...
Code
This interactive EXCEL workbook demonstrates the Elementary Fourier Optics (EFO) model for instruments that measure surface topography using interference phase. The workbook calculates the expected result for simple object surface profiles as a function of numerical aperture, wavelength, defocus, and other optical parameters. The EFO model is descr...
Article
Full-text available
The pursuit of low noise in optical instruments for areal surface topography measurement is relevant to many surface types, ranging from super-polished optical surfaces to weakly reflecting or scattering textures that require enhanced signal sensitivity. We clarify the definition and experimental methods for quantifying random noise in areal surfac...
Article
Full-text available
We propose a practical theoretical model of an interference microscope that includes the imaging properties of optical systems with partially coherent illumination. We show that the effects on measured topography of a spatially extended, monochromatic light source at low numerical apertures can be approximated in a simplified model that assumes spa...
Patent
Full-text available
Physical devices for facilitating wearable virtual and/or augmented reality (VR/AR) typically employ stacks containing multiple parallel plates. The parallel plates within the stack may have features and coatings applied to their surfaces to act as waveguides such that, when the device is placed in front of a user’s eye, light information from the...
Article
Full-text available
Coherence scanning interferometry is one of the most accurate surface measuring technology, and it is increasingly applied to challenging surface structures, such as additive manufactured part and transparent films, directly in environments that resemble production areas more than metrology labs. Environmental disturbances may further compromise me...
Patent
Full-text available
Measurement of cylinder shaft lead angle using areal topography measurement means and methods
Conference Paper
Full-text available
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...
Presentation
Full-text available
This is a presentation of Zygo Corporation delivered during a commercial session. It is a quick introduction to the company on the occasion of its 50th anniversary.
Conference Paper
Full-text available
Interferometers for the measurement of surface form and texture have a reputation for high performance. However, the results for many types of surface features can deviate from the expectation of one cycle of phase shift per half wavelength of surface height. Here we review the fundamentals of imaging interferometry and describe ways of defining in...
Article
Full-text available
This review gathers together 15 special topics in modern interferometric metrology representing a sampling of historical, current and future developments. The selected topics cover a wide range of applications, including distance and displacement measurement, the testing of optical components, interference microscopy for surface structure analysis,...
Article
Full-text available
A revolutionary development in optical displacement metrology has been the transition from free-space laser interferometers to extreme-precision optical encoders for positioning measurements in semiconductor photolithography systems. An increasingly demanding error budget for stage motion control has mandated a dramatic reduction in sensitivity to...
Article
Full-text available
Das Funktionsverhalten von Dichtflächen und Lagern hängt von der Strukturrichtung in Bezug auf die Drehachse eines bearbeiteten Teils ab, dem sogenannten Verdrehwinkel oder Steigungswinkel. Wir präsentieren unsere Lösung für die Messung von Drallwinkeln mit Hilfe von Interferenzmikroskopie, in mehrachsiger Ausführung und MX Softwarepaket zur Bestim...
Conference Paper
Many modern products require surfaces with highly complex surface topographies, often involving high slope angles, a mix of random and deterministic texture and freeform underlying geometries (see Fig. 1). In this presentation, we will show a range of recent developments that allow such complex features to be measured and highlight some remaining i...
Presentation
Full-text available
A brief tutorial on the meaning and use of the Instrument Transfer Function to describe the response of optical surface topography measuring systems
Data
These are the original presentation slides from "Interpreting interferometric height measurements using the instrument transfer function," presented at the FRINGE conference in Stuttgart, 2005.
Preprint
Full-text available
Optical fabrication relies on precision metrology over a wide range of lateral scales. Consequently, an important performance parameter for Fizeau interferometers is the instrument transfer function (ITF), which specifies the system response as a function of surface spatial frequency. Advances in test procedures, instruments and automated analysis...
Preprint
Full-text available
Optical systems for immersive displays incorporate a range of optical components and assemblies that require precision non-contact metrology, including Fizeau interferometry of surface form, new techniques for aspheric microlenses, and interference microscopy for surface structure and texture analysis. Here we consider the problem of evaluating the...
Conference Paper
Full-text available
Optical fabrication relies on precision metrology over a wide range of lateral scales. Consequently, an important performance parameter for Fizeau interferometers is the instrument transfer function (ITF), which specifies the system response as a function of surface spatial frequency. Advances in test procedures, instruments and automated analysis...
Presentation
Update! For the most recent version of the tutorial, please view the ASPE Tutorial 2020 presentation. This tutorial is for precision engineers interested in optical methods of dimensional metrology—size, form, texture, position. Part 1 covers geometrical optics and the foundations of optical systems, telescopes, autocollimators, alignment scopes,...
Article
Full-text available
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Article
Full-text available
https://www.azooptics.com/Article.aspx?ArticleID=1264
Conference Paper
Full-text available
Coherence scanning interferometry (CSI) is widely used for surface topography characterisation. With the ability to measure both rough surfaces with the high slopes and optical finishes, CSI has made contibutions in fields from industrial machining to optical fabrication and polishing [1,2]. While the low coherence sources for CSI are typically bro...
Presentation
Full-text available
German presentation exercise at a Goethe Institute, describing my experiences in vision health in Ghana in 2011.
Conference Paper
Full-text available
A common task in surface metrology is the calibration of the measuring instrument's height scale. There are many techniques for calibration, ranging from interferometry at a known wavelength [1] to the use of material measures that have been certified using a primary instrument at a National Metrology Institute [2-4]. A common technique relies on a...
Conference Paper
Full-text available
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 con...
Conference Paper
Full-text available
Characterizing the limits of resolution requires an adjustment in our vocabulary. It would be preferable in specification sheets and technical reports to reserve “resolution” for those metrology attributes that are constrained by our ability to clearly separate neighboring features or surface depths, as in 2D and 3D imaging. For distance measuremen...
Book
Full-text available
In 2015, an online community of scientists and mathematicians got together to share a love of equations, and, every day that year, a beautiful equation appeared on Facebook. The page has since attracted almost 6000 "likes", showing that lots of other people love equations as much as we do. What do we mean by "beautiful" in the context of equations?...
Patent
Full-text available
A method for determining information about an object including a curved portion and a planar portion, the curved portion having a first curved surface having an apex and defining an axis of the object, includes: directing measurement light to the object; detecting measurement light reflected from the first curved surface of the curved portion; dete...