Preface

After four centuries a quote from Galileo Galilei is still the most effective way to introduce a Metrology book: "Measure what is measurable, and make measurable what is not so". Every human activity needs an objective measurement and every global process should be supported by a common standard.

There are several handbooks, tutorials and journals that focus on the basic concepts of metrology, the uncertainty theory and the international reference standards. Moreover, the engineering literature is awash with measurement methods for each specific field. The aim of this book is different: it offers the most recent developments in some key sectors, its goal is to represent the state of art in the main metrological areas. This book is a combination of seventeen scientific publications, written in a rigorous and eloquent style by academic authors from five continents. Not only will you find highlights of important technological contributions, you will also learn about some current critical issues and relative proposals to improve the future steps. The script is directed both to students/researchers and professionals.

The volume is organized in six sections:


#### XII Preface


– Sixth section (Biology and Medicine) carries the reader through advances of metrology applications in biotechnology and dentistry. First chapter is focused on technical issues in metrology for biology; it describes recent methods for quantitation of deoxyribose nucleic acids and characterization techniques for various biologic measurands like proteins, cells, microorganisms, and glycans. Second chapter examines main methods for 3D measurement of free form oral surfaces; specifically, it considers the width of the crown preparation margin, the angulation of the margin and the taper angle formed when a tooth is prepared for a crown.

X Preface

– Third section (Voltage, Current and Frequency) examines some electrical/electronic measurements. First chapter describes the modern voltage metrology which is based on Josephson junctions; the extension of DC Josephson voltage standard to AC and the most advanced solutions in terms of integration, power dissipation and noise immunity. Second chapter focuses on power measurements under non-sinusoidal waveform conditions; harmonic voltage, harmonic current, and harmonic power at industrial frequency, with aspects such as its principle, setup, uncertainty evaluation, and experimental validation also covered. Third chapter provides calibration methods of RF and microwave power sensor with system setup, modeling, equations, and analyses in different representations, traceability and measurement uncertainty evaluations. Fourth chapter presents a fast method for frequency measurement by rational approximations with application in Mechatronics; theoretic operation principle, experimental and simulation results for the frequency measurement method are

– Fourth section (Optics) provides direction for the measurement of optical radiation under different configurations and for several applications. First chapter is an accurate introduction to optical metrology, it involves all necessary bases: international terminology, predominant quantities, geometrical relationship, standards, uncertainties, photometers, spectrometers and light sources. Second chapter is devoted to consideration of metrological aspects of intrinsically interconnected characteristics of light fields, such as intensity, polarization and coherence; further it represents both experimental and data processing techniques leading to high-sensitive and reliable diagnostics of biological tissues. Third chapter is oriented toward recent digital signal processing techniques used in interferometry; it reviews digital demodulation algorithms for interferometric metrology systems and presents a new (unpublished) digital demodulation algorithm. Fourth chapter explains phenomena about light sources with short and ultra-short pulse duration; it discusses the parameters of the driving laser: pulse duration, pulse energy, photon energy, and the number of attosecond bursts (single pulses or a train). Fifth chapter reports some characterization techniques about femtosecond/picosecond optical pulses measurement (autocorrelation and

– Fifth section (Time and Relativity) is based on tools/methods for measuring time and relativistic metrology. First chapter gives an historical review, the algorithms to define the orbit of the spacecraft by ground-based measurements and the techniques used to forecast Earth rotation parameters. Second chapter canvases relativistic metrology in terms of standards and conventions used to describe physical phenomena on the Earth's surface and space physics near the Earth and

presented in a wide frequency range.

Wavelet transform).

in the Solar System.

Special thanks to authors for their concerted efforts and to my mother for her continuous encouragement.

**Luigi Cocco, PhD** 
