International and National Journals
A. Balsamo, A. Chimienti, S. Desogus, P. Gattoni, A. Meda, R. Nerino, G. Pettiti, M.L. Rastello, M. Spertino
A portable stereovision system for cultural heritage monitoring
CIRP Annals-Manufacturing Technology, Vol. 54/1, pp. 499-502, 2005.
In a nation wide project named SIINDA, a novel instrument was developed and tested, intended for monitoring and diagnosing monuments. The instrument -named AVS- is portable to operate on field, and is capable of measuring 3D and colorimetric coordinates simultaneously. The paper describes the AVS, with a focus on its geometric measurement capability. Particular attention is given to the software compensation of the geometrical errors: the model is given, and the experimental plan to derive the model parameters is described, including the artefact designed and made for this purpose. Experimental results of laboratory and of on field tests are reported.
A. Balsamo, G. Mana, F. Pennecchi
On the best fit of a line to uncertain observation pairs
Metrologia, Vol. 42 (5), pp. 376-382, 2005.
An analysis is made of minimum variance estimates when both the independent and dependent model-variables are uncertain. The simplest of these estimation problems, concerning the best fit of a line to a set of uncertain observation pairs, can be solved analytically. This paper analyses in detail this problem, compares the different solutions and shows there are different ways to solve the same optimization problem. Particular emphasis is given to the uncertainty of the estimates.
A. Pasquini, G.B. Picotto, M. Pisani
STM carbon nanotube tips fabrication for critical dimension measurements
Sensors and Actuators A-Physical, Vols. 123-124, pp. 655-659, 2005.
Reconstruction errors due to the finite shape of the tip remain the major limitation of Scanning Probe Microscopy for nanometer scale measurements. Carbon Nanotubes are ideal SPM probes thanks to their nanometric diameter, high aspect-ratio and strength. In this work, the feasibility of a method to attach CNT on the apex of a Tungsten tip has been tested. By the fabricated CNT tip we successfully imaged a metalized rectangular grating obtaining a profile nearly rectangular in comparison with classic STM-W tip. The metallic behavior of CNT was also analyzed from the I-V characteristic of the tunneling current.
L.S. Ma, Z. Bi, A. Bartels, L. Robertsson, M. Zucco, R. Windeler, G. Wilpers, C. Oates, L. Hollberg, S. Diddams
International comparisons of femtosecond laser frequency combs
IEEE Transactions on Instrumentation and Measurement, Vol. 54, no. 2, pp. 746-749, 2005.
Two types of international comparisons of femtosecond laser frequency combs have been performed in France and the USA. Five combs were involved in the comparisons. Three combs, of which two are transportable, employ nonlinear photonic crystal fiber (PCF) to obtain a wide spectrum covering a full optical octave. The other two are based on broadband femtosecond lasers and require no PCF. The comparisons were performed by counting the optical heterodyne beats between pairs of combs. The frequency agreement among three combs was at the subhertz level in the 563 THz part of the comb spectrum when the combs were referenced to a hydrogen maser. When the combs were referenced to an optical standard, the frequency agreement among four combs was much improved and found to be at the ˜ 10-19 level in the spectral range of 333-473 THz. The fact that this result is obtained by five independent measurement systems (combs) strengthens the conclusion that no systematic effects are present at this level.
L. Robertsson, M. Zucco, L.S. Ma, O. Terra, F. Saraiva, S. Gentil, C. Chekirda, Yu Zakharenko, V. Fedorin, L. Mostert
Results from the CI-2004 campaign at the BIPM of the BIPM.L-K11 ongoing key comparison
Metrologia, Vol. 42, Tech. Suppl., 04002, 2005.
L. Robertsson, M. Zucco, L.S. Ma, Quin Jin, Liu Xiuying, Liu Zhongyou, J.P. Wallerand, S. Van den Berg, Reine Johansson, Håkan Skoogh
Results from the CII-2004 campaign at the BIPM of the BIPM.L-K11 ongoing key comparison
Metrologia, Vol. 42, Tech. Suppl., 04003, 2005.
L. Robertsson, M. Zucco, L.S. Ma, J. Henningsen, J. Hald, C. Bandis, A. Duta, D. Boiciuc, D. Georgescu, R. Fira, P. Dorsic
Results from the CI-2005 campaign at the BIPM of the BIPM.L-K11 ongoing key comparison
Metrologia, Vol. 42, Tech. Suppl., 04004, 2005.
A. Lazzari, A. Balsamo, E. Savio
I sistemi di misura ottici per il controllo dimensionale
Tutto Misure, anno VII, n. 3, pp. 219-222, 2005.
Si assiste in questi anni ad un sempre maggior sviluppo ed utilizzo dei sensori senza contatto per il controllo dimensionale. Ciò è dovuto all'incontro, reso oggi possibile dalla tecnologia., fra esigenze di accuratezza e di velocità di misurazione. Inoltre, tali sensori operano con forze di contatto nulle e sono quindi idonei a misurare anche oggetti flessibili e/o leggeri. L'articolo opera una classificazione, e descrive le caratteristiche peculiari dei sensori senza contatto, soffermandosi in particolare sulla loro integrazione con le CMM (Macchine di Misura a Coordinate).
G.E. D'Errico
Motori lineari
Macchine Utensili, pp. 44-48, giugno 2005.
Conference Proceedings
A. Meda, A. Balsamo
Error correction of a triangulation vision machine by optimization
Published as short communication in Proceedings of the VII Advanced Mathematical and Computational Tools in Metrology (AMCTM), P. Ciarlini, E. Filipe, A.B. Forbes, F. Pavese, C. Perruchet, B. Siebert (editors), pp. 316-319, World Scientific Publishing 2006.
This paper reports the error model, the identifiability study of its parameters, its software simulation and the experimental validation used to compensate the error of a triangulation vision machine (AVS-Active Vision System) intended for monitoring and diagnosing monuments and other Cultural Heritage. A careful alignment is required but not sufficient to achieve the sought performance. In addition, operation in open air - where temperature fluctuations up to ±15 K are expected - and transportation would require realignment on the spot. As the errors resulting from misalignment are highly repeatable, they are best compensated in software.
M. Bisi, E. Massa, A. Pasquini, G.B. Picotto, M. Pisani
Nanometrology at the IMGC. Nanoscale calibration standard and methods
Ed. G. Wilkening, L. Koenders, WILEY-VCH, Weinheim, pp. 22-36, 2005.
A survey of the nanometrology-related activities in progress at the Istituto di Metrologia "G. Colonnetti" (IMGC) is presented. Some special apparatus for critical measurements in the nanoscale range are described. The development of instrumentation and methods for quantitative Scanning Probe Microscopy, optical diffractometry and atomic scale displacement metrology by combined X-ray and optical interferometry is outlined. Focus is given on calibration and methods for traceable measurements, high resolution positioning and sub-nanometer displacements measurements.
A. Pasquini, G.B. Picotto, M. Pisani
STM tips fabrication for critical dimension measurement
Proceedings of NATO Advanced Study Institute on Scanning Probe Microscopy: Characterization, Nanofabrication and Device Application of Functional Materials, Algarve (Portugal), October, 2002, Ed. P.M. Vilarinho, Y. Rosenwaks, A. Kingon, 2005: Vol. 186, p. 488.
In this contribution a method is described for sharpening Tungsten (W) tips through a two-step electrochemical etching. In the first step, under strong reaction conditions, we obtain a long hyperbolic cone, while in the second with a micropositioner we bring only the apex of the first cone in contact with a thin film of etchant. In this way, controlling the meniscus height with an optical microscope, only the very end of the tip is etched. Some processing parameters such as the rate of the electrochemical reaction of erosion of the W wire, related to the electrolyte concentration and to the applied voltage, the length of the wire immersed in the solution and the shape of the meniscus have been investigated. Both direct current (DC) and alternating current (AC) were tested, observing two different ways of W wire erosion. The fabrication process provides very sharp tips, tips with radius of curvature below 10nm and cone angle aperture within 30º have been obtained in some cases. Further improvements are in progress, namely to extend the tip-shape repeatability as given by the two-step process. Some promising STM images of diffraction gratings have been obtained using tips fabricated with this process.
A. Balsamo, A. Chimienti, P. Grattoni, A. Meda, R. Nerino, G. Pettiti, M.L. Rastello, M. Spertino
Architectural surface monitoring by means of the active vision system "AVS"
Proceedings of CIPA 2005 - XX International Symposium Torino - International Cooperation to Save the World´s Cultural Heritage, pp. 101-106, Turin, September 2005.
Monitoring of the conservation degree of art pieces is essential in Cultural Heritage management. It allows to detect possible degradation phenomena and to prevent their occurrences, thus saving art pieces and money. It requires repeated measurements of relevant parameters of an art piece, to monitor their evolution over time. In the field of interest of architectural surfaces (monument, statues, …), frescoes and paintings, two groups of the very important parameters are about geometric and colorimetric information. To enable the detection of surface changes at a given resolution (e.g. erosion, mould growth, chemical alterations, …), geometric and colorimetric measurements must be sufficiently accurate and integrated to each other. A preliminary condition for this to occur, especially for colorimetric measurements, is reproducing the same measurement conditions (surveying geometry, color temperature of the light sources, test point localization, …) in subsequent measuring sessions. Indeed, results of color measurement of a test point on a painted surface may change significantly with small shifts of the measuring device position. On the other hand, use of landmarks to mark these points is not always possible for obvious reasons, so monitoring may become a tricky task. The Active Vision System (AVS), specifically designed for acquiring and monitoring frescoes and architectural surfaces, overcomes these problems. AVS performs integrated colorimetric and geometric accurate measurements in a range ˜ (3 - 8) m and with a field of view ˜ (6 x 4) m2 at 8 m. Thanks to its computerized control of the operations, it can record both the results and the setup parameters of measurement, i.e.: relative position between instrument and scene, integration time, fixation angles, spatial resolution of the cameras, artificial light positioning. This way, AVS can recover the measuring setup in subsequent measuring sessions, and repeat the measurement automatically. In addition, it can process the acquired data on-field and compare the results with previous ones (monitoring), so avoiding possible waist of time and money due to postponing analyses to laboratory, as with traditional procedures. After a short description of the AVS system and of its working principle, this paper first describes the procedures to measure and monitor surface geometry and color. Then it presents the results obtained in laboratory tests, and compares them with a commercial laser scanner and a tristimulus colorimeter.
A. Meda, A. Balsamo, D. Corona, E. Audrito
Compensazione software degli errori di geometria di una macchina di misura senza contatto a triangolazione (SVA)
Atti del IV Congresso Metrologia e Qualità, pp. 299-305, Torino, febbraio 2005.
Il Sistema di Visione Attivo (SVA) è una macchina di misura a coordinate senza contatto in grado di eseguire misurazioni dimensionali e colorimetriche con caratteristiche metrologiche. Per le dimensioni del suo volume di lavoro ((10 x 6 x 3) m3 circa ), si colloca in un campo di applicazione intermedio tra sistemi di scansione laser e sistemi fotogrammetrici. La macchina è nata per scopi di monitoraggio di affreschi nell'ambito del Progetto Finalizzato Beni Culturali del CNR, ed è poi stata perfezionata nel corso del progetto nazionale SIINDA (Sistemi Innovativi di Indagine e Diagnosi Assistita) avente per caso di studio il teatro romano di Aosta. L'elemento di rivelazione delle coordinate è una coppia di telecamere poste a distanza nota, montate ognuna su una tavola rotante e solidali entrambe ad un corpo orizzontale rotante; le telecamere sono in grado di ruotare in maniera tale da puntare entrambe allo stesso bersaglio posizionato un nello spazio. Nonostante l'elevata accuratezza dei componenti meccanici, si pone un problema di riduzione degli errori di misura sistematici. Tale problema è accentuato dal fatto che la macchina è portatile ed è quindi sottoposta a urti ed escursioni termiche durante il trasporto sul luogo di utilizzo. Ad ogni spostamento sarebbe allora necessaria una messa in punto manuale della macchina, che comporterebbe però un'enorme spesa in tempo. Per questo motivo, è nata la necessità di sviluppare una procedura di compensazione software degli errori di geometria della macchina, la più possibile rapida nell'esecuzione, in modo da renderla praticabile prima dell'uso in campo.
Technical Reports
M. Pisani
Satellite-Satellite Interferometer Mission for determination of the Earth's Gravity Field: report on laboratory test on angular and lateral displacement sensors
IMGC Technical Report no. 135, November 2005.
A study about the feasibility of a space mission for the determination of the Earth gravity field has been carried out by Alenia Spazio with the collaboration of IMGC. The mission is based on two satellites on the same orbit at an altitude of about 325 km, 10 km distance one to the other, each one carrying a free falling mass which orbit is influenced by the gravity field. The distance variations between the two free falling mass-carrying information about the gravity field anomalies- is measured by means of a laser interferometer. The relative orientation of the two satellites and the laser beam must be controlled by means of angular and displacement sensors which make use of the laser beam itself as a reference. Herein are presented the results of experimental tests made to verify the measurement principle and the ultimate performance of these sensors.
G.E. D'Errico, M. Pisani
Effetto Casimir: introduzione e approcci sperimentali
Rapporto Tecnico IMGC n. 136, novembre 2005.
Si introduce un insieme di fenomeni noti sotto l'appellativo di effetto Casimir, dal nome del fisico che ne predisse e anticipò alcuni sviluppi attuali. Allo stato dell'arte, si trovano recentissimi interessi teorici e applicativi in diversi campi industriali, che spaziano dai dispositivi nanotecnologici, all'ingegneria della superficie, alla tribotecnica. Se ne delineano i principi fisici basilari e si focalizzano alcuni aspetti notevoli dal punto di vista metrologico. Si tracciano alcune prospettive di rilevanza esemplificativa (sintesi di proprietà avanzate di film sottili e problemi di frizione in sistemi elettromeccanici miniaturizzati). In termini di ricadute scientifiche per l'avanzamento delle conoscenze fisiche e delle opportunità di innovazione che si attendono per il prossimo futuro, viene a risaltare il ruolo dello sviluppo di tecniche di misura di precisione dell'effetto. Alcuni approcci sperimentali sono presentati in una prospettiva di laboratorio di metrologia.
D. Corona, M. Pisani
Software di acquisizione per il campione nazionale d'angolo
Rapporto Tecnico IMGC n. 147 dicembre 2005.
Il software per la acquisizione e la gestione dei dati inviati dall'autocollimatore utilizzato nella stazione di taratura per i campioni d'angolo è descritto e analizzato.