RT Journal Article T1 Near-field diffraction-based focal length determination technique A1 Torcal Milla, Francisco José A1 Sánchez Brea, Luis Miguel AB An accurate and simple technique for determining the focal length of a lens is presented. It consists of measuring the period of the fringes produced by a diffraction grating at the near field when it is illuminated with a beam focused by the unknown lens. In paraxial approximation, the period of the fringes varies linearly with the distance. After some calculations, a simple extrapolation of data is performed to obtain the locations of the principal plane and the focal plane of the lens. Thus, the focal length is obtained as the distance between the two mentioned planes. The accuracy of the method is limited by the collimation degree of the incident beam and by the algorithm used to obtain the period of the fringes. We have checked the technique with two commercial lenses, one convergent and one divergent, with nominal focal lengths (+100±1) mm and (−100±1) mm respectively. We have experimentally obtained the focal lengths resulting into the interval given by the manufacturer but with an uncertainty of 0.1%, one order of magnitude lesser than the uncertainty given by the manufacturer. PB Elsevier SN 0143-8166 YR 2017 FD 2017-05 LK https://hdl.handle.net/20.500.14352/18972 UL https://hdl.handle.net/20.500.14352/18972 LA eng NO [1] Picht J. Mess-und prüfmethoden der optischen fertigung, 1. Berlin, Germany:Akademie-Verlag; 1955.[2] Flügge J. Einführung in die Messung der optischen Grundgrößen. Karlsruhe,Germany: G. Braun; 1954.[3] Dörband B, Gross H, Müller H. Handbook of optical systems. Metrology of opticalcomponents and systems, 5. Weinheim, Germany: John Wiley & Sons; 2012.[4] Malacara D. Optical shop testing. Wiley series in pure and applied optics. Hoboken,United States: Wiley; 2007.[5] Nakano Y, Murata K. Talbot interferometry for measuring the focal length of a lens.Appl Opt 1985;24:3162–6.[6] Jin X, Zhang J, Bai J, Hou C, Hou X. Calibration method for high-accuracymeasurement of long focal length with Talbot interferometry. Appl Opt 2012;51:2407–13.[7] de Angelis M, de Nicola S, Ferraro P, Finizio A, Pierattini G. Analysis of moirefringes for measuring the focal length of lenses. Opt Lasers Eng 1998;30:279–86.[8] Keren KM, Kreske E, Kafri O. Universal method for determining the focal length ofoptical systems by moire deflectometry. Appl Opt 1998;27(8):1383–9.[9] Trivedi S, Dhanotia J, Prakash S. Measurement of focal length using phase shiftedmoiré deflectometry. Opt Lasers Eng 2013;51(6):776–82.[10] Rasouli S, Rajabi Y, Sarabi H. Microlenses focal length measurement using z-scanand parallel moiré deflectometry. Opt Lasers Eng 2013;51(12):1321–6.[11] Lee S. Talbot interferometry for measuring the focal length of a lens without moirefringes. J Opt Soc Korea 2015;19:165–8.[12] Miks A, Pokorny P. Use of diffraction grating for measuring the focal length anddistortion of optical systems. Appl Opt 2015;54(34):10200–6.[13] Wu J-j, Chen J-b, Xu A-c, Gao X-y, Zhuang S. Focal length measurement based onHartmann–Shack principle. Opt – Int J Light Electron Opt 2012;123(6):485–8.[14] Tebaldi M, Forte G, Torroba R, Bolognini N, Tagliaferri A. Self-imaging pitchvariation applied to focal length digital measurements. Opt Commun 2005;250(1):10–5.[15] Mikš A, Pokorny` P. Edge spread function of Talbot phenomenon. Opt – Int J LightElectron Opt 2016;127:8065–9. http://dx.doi.org/10.1016/j.ijleo.2016.06.003.[16] Talbot HF. Lxxvi. Facts relating to optical science. No. iv. Lond Edinb Philos Mag JSci 1836;9(56):401–7.[17] Patorski K. I. The self-imaging phenomenon and its applications. Prog Opt1989;27:1–108.[18] Torcal-Milla FJ, Sánchez-Brea LM, Salgado-Remacha FJ, Bernabeu E. Self-imagingwith curved gratings. Opt Commun 2010;283(20):3869–73.[19] Torcal-Milla FJ, Sánchez-Brea LM, Bernabeu E. Near field diffraction of cylindricalconvex gratings. J Opt 2015;17(3):035601.[20] Morrison FA. Obtaining uncertainty measures on slope and intercept of a leastsquares fit with excel linest. Michigan, USA: Department of Chemical Engineering,Michigan Technological University, Houghton; 25 September 2014.[21] Sánchez-Brea LM, Torcal-Milla FJ, Herrera-Fernandez JM, Morlanes T, BernabeuE. Self-imaging technique for beam collimation. Opt Lett 2014;39(19):5764–7.[22] Christensen R. Linear models for multivariate, time series, and spatial data. Berlin:Springer-Verlag; 1985.[23] Cressie N. Statistics for spatial data, revised ed., vol. 928. New York: Wiley; 1993.[24] Sánchez-Brea LM, Torcal-Milla FJ, Bernabeu E. Variogram-based method forcontrast measurement. Appl Opt 2007;46(22):5027–33. NO © 2016 Elsevier Ltd. All rights reserved.The authors thank J.A. Gomez-Pedrero for his help in this work. This work has been supported by project SPIP2015-01812 of the Ministerio de Interior of Spain and by SEGVAUTO- TRIES CM S2013/MIT-2713 of the Dirección General de Universidades e Investigación, Comunidad de Madrid (Spain). NO Ministerio del Interior, España NO Dirección General de Universidades e Investigación, Comunidad de Madrid (Spain) DS Docta Complutense RD 1 may 2024