An International Peer Reviewed Research Journal
Frequency : Monthly,
ISSN : 0971 – 3093
Editor-In-Chief (Hon.) :
Dr. V.K. Rastogi
e-mail:[email protected]
[email protected]

 AJP SSN : 0971 – 3093
Vol 31, No 1, January, 2022

Journal of Physics

A Special Issue in the Memory
Late Prof B N Gupta

Guest Edited By : R S Sirohi & A K Nirala

Anita Publications
FF-43, 1st Floor, Mangal Bazar, Laxmi Nagar, Delhi-110 092, India

Guest Editorial

This special issue in memory of Prof Baij Nath Gupta contains 14 papers, of which seven papers are in optics, two are in spectroscopy, two are in electronics, two are in material science and one in biomedical field.
Sirohi describes the various methods that have been utilized for the measurement of focal length along with the uncertainty of measurement. Focal length is an important parameter of all the image forming optical instruments. Kumar et al have carried out simulation studies of correction of haze corrupted images. They use an iterative technique of Gamma correction for generating differently exposed images and fusing these images with the proposed multi-resolution fusion scheme. Comparison with existing methods is also carried out. Roy and Chaudhuri present an analytical description of a single mode fiber for temperature sensing. There are two papers on frequency up-conversion using excitation radiation from diode lasers operating at 980nm and 808nm. Kumar et al have studied up-conversion emission in Ho3+/Yb3+ co-doped YF3+ phosphor material with 980nm excitation radiation. The phosphor material is synthesized via hydrothermal method using aqueous tri-sodium citrate as solvent. Up-conversion is observed at emission bands around 543nm, 650nm, and 743nm. These emission bands are assigned to the 5F4 / 5S2 → 5I8, 5F5 → 5I8 and 5I4 → 5I8 transitions, respectively of Ho3+ ion. Dey and Rai have studied Er3+/Er3+ – Yb3+ doped/co-doped La2O3 phosphor with 980nm excitation and 808nm excitation. They have also discussed up-conversion emission spectra of several other phosphor systems and applications of these. There are two papers on electronics. Paper by Rana et al presents a time-varying-pole radius (TVPR) infinite impulse response (IIR) multi-notch filter (MNF) design for simultaneously balancing the trade-off between transient duration and quality factor. The proposed TVPR IIR MNF design offers superior results over the traditional and recently reported MNF designs. Paper by Sehgal et al presents a novel application of a Nonlinear Proportional-Integral-Derivative (NPID) controller to effectively attain the maximum power point tracking (MPPT) for proton exchange membrane fuel cell (PEMFC). Proposed NPID controller is based on basic structure of PID controller wherein its proportional and integral term gains can vary according to instantaneous error and its rate of change at run time.
Ghosh et al carried-out speckle photography using a single hololens as an imaging system for one-to-one imaging. Singh et al have carried out simulation studies of crack tip opening displacement (CTOD) and stress intensity factor (SIF) on an aluminum beam specimen using ANSYS software and compared the results with those obtained earlier experimentally using speckle photography. Further, the simulation results for different fracture parameters as a function of load have been obtained. Pathak et al used close aperture Z-scan technique to obtain non-linear refractive index of O+ blood. They also demonstrate that CA Z-scan technique could be used to obtain concentration of hemoglobin in any blood type. Laser speckles have also been used to examine bioactivity in pomegranate by Koley and Nirala. They have used image processing algorithms such as time history of speckle pattern (THSP), inertia moment (IM), absolute value of differences (AVD), Fujii and Fujii, to evaluate the biospeckle activities and contrast, correlation, energy, and homogeneity for texture analyses of the two regions of interest of pomegranate. There are two papers on material science. Organic semiconductors based on chrysene derivatives are used for several applications in optoelectronic industries. Khatau and Sahu have computed the optical absorption spectra of some chrysene derivatives using time-dependent density functional theory. The absorption spectra of these compounds lie in the range 200nm to 333nm. Transparent electrodes (TEs) are utilized in many electronic devices such as displays, solar cells, touch screens etc. Bharti et al present a computational approach to calculate the percolation threshold and transmittance of nanowire network based transparent electrodes.
Ramagopal has presented a review article on single point diamond turning (SPDT) which is used for fabricating aspherical surfaces with high precision. The article examines some critical issues that determine the outcome of SPDT process.
In the end, we thank all the authors who accepted our invitation and submitted their manuscripts in time. Without their cooperation the present special issue would not have seen the light of the day. Finally, we would like to thank the editorial team for their tremendous efforts during this period. We are also grateful to Er Manoj, Ms Ashmita Singh and Ms Laxmi for their tireless work during this period.
The special issue has papers of interest, and we are extremely pleased to submit it for general readership.

Rajpal Sirohi
A K Nirala

About Professor B N Gupta

Baij Nath Gupta
Baij Nath Gupta

Prof. Baij Nath Gupta was born on March 31, 1942. He obtained his B Sc (Physics, Maths & Statistics) & M Sc (Physics) from Agra University in 1962 & 1964, respectively. He completed his M Tech in Applied Optics & Ph D (Physics) from the Indian Institute of Technology, Delhi, in 1968 & 1972, respectively. Prof Gupta first began his extensive career as Sr Design Engineer in 1977 at IIT Delhi, where he was promoted to Chief Design Engineer in 1986. He subsequently took over the role of Head, Instrument Design Development Centre (IDDC), and promoted to Professor at IIT Delhi in 1995.
He joined as Director, Netaji Subhas Institute of Technology (NSIT), Delhi, in 1997, where his tenure lasted for about six years. He re-joined IIT Delhi as a Professor after his term in NSIT Delhi. His field of specialization being Instrumentation, Prof Gupta supervised 5 Ph D thesis and guided over 18 M Tech & 3 M Sc projects. His teaching experience covered a large stretch of about 18 years in IIT Delhi. Prof Gupta published about 40 research papers in referred journals and presented thirty research papers in national/International seminars and conferences. He completed four externally sponsored research projects and ten consultancy projects. He was a member of four professional bodies including Optical Society of America. In addition he was instrumental in developing eight instruments at IDD Centre, IIT Delhi. He had numerous awards & distinctions to his credit, including the Fellowship Award by Society for Information Sciences, India (1995); Eminent Engineer Award by Institution of Engineers, India (2001); Giants Gaurav Samman by the Giants International (2001); Super Brain of India Award by Competition Success Review (CSR); Shiromani Purskar by Institute of Economic Studies, New Delhi; and the Best Citizens of India Award by the International Publishing House.
Throughout his career, Prof Gupta had been the Chairman of various governing bodies & committees, and member of nearly twenty two prestigious committees, including ISTE, Delhi Section for two years, and the National Standing Committee (NSC) on Rural Technology of CAPART for six years for conducting social works etc. He was also the Founder Director of Mahila Institute of Technology, Delhi. Prof Gupta has been continuously evolving in step with rapidly advancing technology to retain its technological edge in Centre for Sensors, Instrumentation, and Cyber-Physical System Engineering (SeNSE) (formerly IDD Centre), IIT Delhi.
He left for heavenly abode on October 23rd, 2006 at New Delhi.

About Guest Editors

R S Sirohi
R S Sirohi

Rajpal S Sirohi is currently serving in the Physics Department, Alabama A&M University, Huntsville, Alabama USA. Prior to this (2013-2016), he was the Chair Professor, Physics Department, Tezpur University, Tezpur, Assam, India. He was Distinguished Scholar (2011-2013) in the Department of Physics and Optical Engineering, Rose Hulman Institute of Technology, Terre Haute, Indiana, USA. During 2000-2011, he had been deeply engaged in academic administration and research as Director, IIT Delhi (Dec. 2000-April 2005); Vice-Chancellor, Barkatullah University, Bhopal (April 2005-Sept. 2007); Vice-Chancellor, Shobhit University, Meerut (Oct.2007-March 2008); Vice-Chancellor, Amity University Rajasthan, Jaipur (March 2008-Oct.2009) and Vice-Chancellor, Invertis University, Bareilly (Jan 2011-Oct.2011). He was also Visitor to Teerthanker Mahaveer University, Moradabad (June 2012- June 2013). Prof Sirohi did his Masters in Physics in 1964 from Agra University, and Post M Sc in Applied Optics and Ph D in Physics both from Indian Institute of Technology, New Delhi in 1965 and 1970, respectively. Prof Sirohi was Assistant Professor in Mechanical Engineering Department at Indian Institute of Technology Madras during 1971-1979. He became Professor in the Physics Department of the same Institute in 1979. He superannuated in April 2005 from IIT Delhi.
Prof Sirohi worked in Germany as a Humboldt Fellow at PTB, Braunschweig, and as a Humboldt Awardee at Oldenburg University. He was a Senior Research Associate at Case Western Reserve University, Cleveland, Ohio, and Associate Professor, and Distinguished Scholar at Rose Hulman Institute of Technology, Terre Haute, Indiana. He was ICTP (International Center for Theoretical Physics, Trieste Italy) Consultant to Institute for Advanced Studies, University of Malaya, Malaysia and ICTP Visiting Scientist to the University of Namibia. He was Visiting Professor at the National University of Singapore and EPFL, Lausanne, Switzerland.
Prof Sirohi is Fellow of several important academies/ societies in India and abroad including the Indian National Academy of Engineering; National Academy of Sciences India; Optical Society of America; Optical Society of India; SPIE (The International Society for Optical Engineering); Instrument Society of India and honorary fellow of ISTE and Metrology Society of India. He is member of several other scientific societies, and founding member of Indian Laser Association. Prof Sirohi was also the Chair for SPIE-INDIA Chapter, which he established with co-operation from SPIE in 1995 at IIT Madras. He was invited as JSPS (Japan Society for the Promotion of Science) Fellow and JITA Fellow to Japan. He was a member of the Education Committee of SPIE.
Prof Sirohi has received the following awards from various organizations:
Humboldt Research Award (1995) by the Alexander von Humboldt Foundation, Germany; Galileo Galilei Award of International Commission for Optics (1995); Amita De Memorial Award of the Optical Society of India (1998); 13th Khwarizmi International Award, IROST (Iranian Research Organisation for Science and Technology (2000); Albert Einstein Silver Medal, UNESCO (2000); Dr Y T Thathachari Prestigious Award for Science by Thathachari Foundation, Mysore (2001); Pt. Jawaharlal Nehru Award in Engineering & Technology for 2000 (awarded in 2002) by MP Council of Science and Technology; NRDC Technology Invention Award on May 11, 2003; Sir CV Raman Award: Physical Sciences for 2002 by UGC (University Grants Commission); Padma Shri, a national Civilian Award (2004); Sir CV Raman Birth Centenary Award (2005) by Indian Science Congress Association, Kolkata; Holo-Knight (2005), inducted into Order of Holo- Knights during the International Conference-Fringe 05-held at Stuttgart, Germany; Centenarian Seva Ratna Award (2004) by The Centenarian Trust, Chennai; Instrument Society of India Award (2007); Gabor Award (2009) by SPIE (The International Society for Optical Engineering) USA; UGC National Hari OM Ashram Trust Award – Homi J. Bhabha Award for Applied Sciences (2005) by UGC; Distinguished Alumni Award (2013) by Indian Institute of Technology Delhi; Vikram Award 2014 by SPIE (The International Society for Optical Engineering) USA. His latest award is 2022 SPIE Maria J Yzuel Educated award bestowed by SPIE in 2022.
Prof Sirohi was the President of the Optical Society of India during 1994-1996. He was also the President of Instrument Society of India for three terms (2003-06, 2007-09, 2010-12). He was on the International Advisory Board of the Journal of Modern Optics, UK and on the editorial Boards of the Journal of Optics (India), Optik, Indian Journal of Pure and Applied Physics. He was Guest Editor to the Journals “Optics and Lasers in Engineering” and “Optical Engineering”. He was Associate Editor of the International Journal “Optical Engineering”, SPIE USA during (1999-Aug 2013), and currently is its Senior Editor. He is the Series Editor of the Series on ‘Advances in Optics, Photonics and Optoelectronics’ published by Institute of Physics Publishing, UK. He is also on the Editorial Board of Asian Journal of Physics (AJP). He edited a special issue of AJP (Vol 28, Nos 10-12, 2019) dedicated to Prof Kehar Singh and recently co-edited a special issue of AJP ( Vol 30, No 1, 2021) with Prof B P Pal dedicated to Padma Shree Prof M S Sodha.
Prof Sirohi has 496 papers to his credit with 250 published in national and international journals, 78 papers in Proceedings of the conferences and 168 presented in conferences. He has authored/co-authored/edited thirteen books including five milestones for SPIE. He was Principal Coordinator for 26 projects sponsored by Government Funding Agencies and Industries, has supervised 25 Ph D theses, 7 M S theses and numerous B Tech, M Sc and M Tech theses. Prof Sirohi’s research areas are Optical Metrology, Optical Instrumentation, Laser Instrumentation, Holography and Speckle Phenomenon.

A K Nirala
A K Nirala

Prof Anil Kumar Nirala obtained his Masters in Physics & Ph D (Physics) from the Indian Institute of Technology, Delhi, in 1987 & 1995, respectively. Prof Nirala began his career as Lecturer in 1991 from A N S College, Nabinagar (Aurangabad) and then moved to Indian Institute of Technology (Indian School of Mines), Dhanbad, as Assistant Professor in 2003 and promoted to Associate Professor in 2007 and then to Professor in 2010. He worked as Head of the Department of Physics for more than six years.
His fields of specialization are speckle metrology, interferometry and holography, and biomedical optics. Prof Nirala has supervised seven Ph D theses, 22 M Sc & 2 M Phil Projects and currently supervising several students towards their Ph D degrees. Prof Nirala published 50 papers in journals of international repute and more than 70 conference papers. He had numerous awards & distinctions to his credit, including the National Merit Scholarship from I Sc (1980) to Graduation (Hons.) (1984); (JRF) and (SRF) of CSIR for doing Ph.D. at IIT Delhi; Agency of Industrial Science and Technology (AIST) Fellowship of Japanese Government (1995); (SERC) Fellowship of Department of Science & Technology of Indian Government (1998); (BOYSCAST) Fellowship of Department of Science & Technology of India (1999) and Commonwealth Scholarship, 2003. Prof. Nirala also visited Japan, Germany, and the United Kingdom as a Post-Doctoral cum visiting Fellow. Currently, he is serving as Coordinator-cum-Incharge of Faculty Development Centre under PMMMNMTT, MHRD New Delhi at IIT Dhanbad and has taken many sponsored projects from various agencies, DST, CSIR, UGC, SERB, and MHRD, Govt. of India. Prof Nirala organised a number of International and National conferences and Orientation/Refresher/Training Programmes/Workshop under FDC and has been recently awarded one Mission project of Water Technology Initiative (WTI), DST of nearly forty lakh rupees. He is a life member of several Academic/Professional bodies like Indian Physical Society, Indian Physics Association, Indian Association Physics Teachers, Optical Society of India and Indian Science Congress Association.

Fig 1. Rajpal Sirohi with nobel laureate Klaus von Klitzing
Fig 2. Rajpal Sirohi, Baij Nath Gupta and a participant
Fig 4. (from left) Rajpal Sirohi, T Tschudi, Baij Nath Gupta
Fig 3. (from right) T Tschudi, Baij Nath Gupta, Rajpal Sirohi

Asian Journal of Physics
(A Publication Not for Profit)
Volume 31, No 1 (2022)

Guest Editorial
About Prof B N Gupta
About the Guest Editors

On the methods to determine the focal length of an imaging system: A tutorial approach
Rajpal S Sirohi1

An image dehazing method employing iterative Gamma correction in a multi-resolution fusion framework
Avishek Kumar, Rajib Kumar Jha and Naveen K Nishchal17

Analytical description of etched clad single-mode optical fiber based refractive index sensor for temperature sensing
Protik Roy and Partha Roy Chaudhuri25

Upconversion emission study in Ho3+/Yb3+ co-doped YF3 phosphor
Kumar Shwetabh, Sachin K Maurya, Madan M Upadhyay and K Kumar31

Frequency Upconversion in Er3+ doped/codoped phosphors
Riya Dey and Vineet Kumar Rai37

A time-varying-pole-radius IIR multi-notch filter with non-zero initial conditions for enhanced performance
K P S Rana, Vineet Kumar, Ishita Kochar and Jasmer Singh53

A dp/dt Feedback scheme based GWO optimized nonlinear PID controller for efficient MPPT of PEMFC
Nitish Sehgal, Sunitha George, K P S Rana and Vineet Kumar77

Single hololens imaging configuration in laser speckle photography for in-plane displacement measurement
Abhijit Ghosh, Nishant Kumar and A K Nirala107

Numerical study on the variation of fracture parameters near crack tip
Abhijeet Singh, Shalendra Kumar and Hira Lal Yadav115

Effect of hemoglobin in the nonlinearity of O+ blood group
Nitesh Kumar Pathak, Sunil Kumar Verma, and Umakanta Tripathy123

Non-destructive differentiation of anthracnose infected and fresh regions of pomegranate using biospeckle technique
C Koley and A K Nirala129

Computational approach to study the effect of filler length dispersity on nanowire networks based transparent electrodes
Y Bharti, V Malik and Shruti Aggarwal135

Optical properties of chrysene based organic semiconductor: A DFT study
Rudranarayan Khatua and Sridhar Sahu141

Single point diamond turned aspheric profiles for advanced optical systems:Opportunities and challenges
RamaGopal V Sarepaka145

Asian Journal of Physics Vol. 31, No 1 (2022)1-16

On the methods to determine the focal length of an imaging system: A tutorial approach
Rajpal S Sirohi
Alabama A&M University Normal, Alabama, USA
This article is dedicated to late Prof B N Gupta

Focal length of an imaging system is an important parameter as it determines its gathering power, numerical aperture and resolution. Its determination becomes very difficult as one of the planes is not physically accessible. A number of methods have been developed that measure either the effective focal length or the back focal length. The objective of the present paper is to discuss various methods that have been investigated and reported in the literature. © Anita Publications. All rights reserved.

Keywords: Focal length, Radius of curvature, Nodal slide, Interferometry.

Collimation Methods

  1. Kaul R C, Measurement of focal length through autocollimation method, J Photo-Int & Remote Sensing, 9 (1981)17-20.
  2. Horner J L, Collimation invariant technique for measuring the focal length of a lens, Appl Opt, 28(1989)1047-1048.
  3. Ilev I K, Simple fiber-optic autocollimation method for determining the focal lengths of optical elements, Opt Lett, 20(1995)527-529.

Talbot Interferometry

  1. Nakano Y, Murata K, Talbot interferometry for measuring the focal length of a lens, Appl Opt, 24(1985)3162-3166.
  2. Bernardo L M, Soares O D D, Evaluation of the focal distance of a lens by Talbot interferometry, Appl Opt, 27, (1988)296-301.
  3. Chon-Wen Chang, Der-Chin Su, An improved technique of measuring the focal length of a lens, Opt Commun, 73(1989)257-262.
  4. Der-Chin Su, Chon-Wen Chang, A new technique for measuring the effective focal length of a thick lens or a compound lens, Opt Commun, 78(1990)118-122.
  5. Bhattacharya J C, Aggarwal A K, Measurement of the focal length of a collimating lens using the Talbot effect and the moiré technique, Appl Opt, 30(1991)4479-4480.
  6. Sriram K V, Kothiyal M P, Sirohi R S, Talbot interferometry in non-collimated illumination for curvature and focal length measurements, Appl Opt, 31(1992)75-79.
  7. Sriram K V, Kothiyal M P, Sirohi R S, Direct determination of focal length by using Talbot interferometry, Appl Opt, 31(1992)5984-5987.
  8. Sriram K V, Kothiyal M P, Sirohi R S, Use of a non-collimated beam for determining the focal length of a lens by Talbot interferometry, J Opt (India), 22(1993)61-66.
  9. Yang K, Liao Z, Tao T, Analysis of Talbot image symmetry about Fourier spectrum plane and measurement of focal length, Acta Opt Sin, 14(1994)50-54.
  10. Singh P, Faridi M S, Shakher C, Sirohi R S, Measurement of focal length with phase-shifting Talbot interferometry, Appl Opt, 44(2005)1572-1576.
  11. Jin X, Zhang J, Bai J, Hou Ch, Hou X, Calibration method for high-accuracy measurement of long focal length with Talbot interferometry, Appl Opt, 51(2012)2407-2413.
  12. Hao Chen, Yong He, Jianxin Li, Heng Lu, Measurement of long focal lengths with a double-grating interferometer, Appl Opt, 52(2013)6696-6702.
  13. Luo Jia, Bai Jian, Zhang Jinchun, Hou Changlun, Wang Kaiwei, Hou Xiyun, Long focal-length measurement using divergent beam and two gratings of different periods, Opt Express, 22(2014)27921-27931.

Lau Interferometry

  1. Thakur M, Shakher C, Evaluation of the focal distance of lenses by white-light Lau phase interferometry, Appl Opt, 41(2002)1841-1845.
  2. Tay C J, Thakur M, Chen L, Shakher C, Measurement of focal length of lens using phase shifting Lau phase interferometry, Opt Commun, 248(2005)339-345.
  3. Prakash S, Singh S, Verma A, A low cost technique for automated measurement of focal length using Lau effect combined with Moiré readout, J Mod Opt, 53(2006)2033-2042.

Moiré Deflectometry

  1. Glatt I, Kafri O, Determination of the focal length of nonparaxial lenses by moiré deflectometry, Appl Opt, 26 (1987)2507-2508.
  2. Keren E, Kreske M K, Kafri O, Universal method for determining the focal length of optical systems by moiré deflectometry, Appl Opt, 27(1988)1383-1385.
  3. Trivedi S, Dhanotia J, Prakash S, Measurement of focal length using phase shifted moiré deflectometry, Opt Lasers Eng, 51(2013)776-782.
  4. Nicola S De, Ferraro P, Finizio A, Pierattini G, Reflective grating interferometer for measuring the focal length of a lens by digital moiré effect, Opt Commun, 132(1996)432-436.
  5. Angelis M de, Nicola S De, Ferraro P, Finizio A, Pierattini G, Analysis of moiré fringes for measuring the focal length of lenses, Opt Lasers Eng, 30(1998)279-286.

Shack-Hartmann Principle

  1. Neal D R, Copland R J, Neal D A, Topa D M, Riera P, Measurement of lens focal length using multi-curvature analysis of Shack-Hartmann wavefront data, Proc SPIE, 5523, 243–255, (2004) Current Developments in Lens Design and Optical Engineering V, (14 October 2004);
  2. Wu J, Chen J, Xu A, Gao X, Zhuang S, Focal length measurement based on Hartmann-Shack principle, Optik, 123(2012)485-488.
  3. Senthil Kumar M, Narayanamurthy C S, Kiran Kumar A S, Focal length measurement of microlens array for Shack–Hartmann wavefront sensor using interferometer, Opt Eng, 52(2013)124103; s.
  4. Motka L, Measurement of focal length with SHS, Fine Mech Opt, 59(2014)43-45.


  1. Matsuda K, Barnes T H, Oreb B F , Sheppard C(Jr), Focal-length measurement by multiple-beam shearing interferometry, Appl Opt, 38(1999)3542-3548.
  2. Kumar Y P, Chatterjee S, Technique for the focal-length measurement of positive lenses using Fizeau interferometry, Appl Opt, 48(2009)730-736.
  3. Chen L, Hao J, Chen Z, Guo X, Focal length measurement by fiber point diffraction longitudinal interferometry, Opt Commun, 322(2014)48-53.
  4. Yang Z, Gao Z, Dou J, Wang X, Focal length measurement based on the wavefront difference method by a Fizeau interferometer, Appl Opt, 53(2014)5598-5605.
  5. Yang G, Miao L, Zhang X, Sun C, Qiao Y, High-accuracy measurement of the focal length and distortion of optical systems based on interferometry, Appl Opt, 57(2018)5217-5223.


  1. Zhao W, Sun R, Qiu L, Sha D, Laser differential confocal ultra-long focal length measurement, Opt Express, 17 (2009)20051-20062.
  2. Zhao W, Sun R, Qiu L, Sha D, Laser differential confocal radius measurement, Opt Express, 18, (2010)2345-2360.
  3. Yang J, Qiu L, Zhao W, Wu H, Laser differential reflection-confocal focal-length measurement, Opt Express, 20 (2012)26027-26036.
  4. Wu H, Yang J, Qiu L, Zhao W, Measuring the lens focal length by laser confocal technique, In Proceedings of the SPIE 8916, (2013)89161E-1-10; doi: 10.1117/12.2035803.
  5. Yang J, Qiu L, Zhao W, Li Z, Shao R, Measuring the lens focal length by laser reflection-confocal technology, Appl Opt, 52(2013)3812-3817.
  6. Zhao W, Li Z, Qiu L, Ren H, Shao R, Large-aperture laser differential confocal ultra-long focal length measurement and its system, Opt Express, 23(2015)17379-17393.

Grating Diffraction

  1. Sirohi R S, Kumar H, Jain N K, Focal length measurement using diffraction at a grating, in Optical Testing and Metrology III, C P Grover (ed), Proc SPIE 1332,(1990)50-55.
  2. Lei F, Dang L K, Measurement of the numerical aperture and f-number of a lens system by using a phase grating, Appl Opt, 32(1993)5689-5691.
  3. Cao X, Shen S, Chen J, Focal length measurements with a three-grating system, Proc SPIE 1993, 275-282.
  4. Lei F, Dang L K, Measuring the focal length of optical systems by grating shearing interferometry, Appl Opt, 33 (1994)6603-6608.
  5. Nicola S De, Ferrao P, Finizio A, Pierattini G, Reflective grating interferometer for measuring the focal length of a lens by digital moiré effect, Opt Commun, 132(1996)432-436.
  6. Zhao S, Wen J F, Chung P S, Simple focal-length measurement technique with a circular Dammann grating, Appl Opt, 46(2007)44-49.
  7. Miks A, Pokorny P, Use of diffraction grating for measuring the focal length and distortion of optical systems. Appl Opt, 54(2015)10200-10206.
  8. Torcal-Milla F J, Sanchez-Brea L M, Near-field diffraction-based focal length determination technique, Opt Lasers Eng, 92(2017)105-109.
  9. Yang W, Wang Z, Shen C, Liu Y, Liu S, Li Q, Du W, Song Z, Research on Focal Length Measurement Scheme of Self-Collimating Optical Instrument Based on Double Grating, Sensors, 20(2020)2718; doi:10.3390/s20092718

Novel Methods

  1. Howland B, Proll A F, Apparatus for the accurate determination of flange focal distance, Appl Opt, 11(1970)1247-1251.
  2. Nemec J, Measurement of focal length, Fine Mech Opt, 16(1971)12-25.
  3. Pernick B J, Hyman B, Least-squares technique for determining principal plane location and focal length, Appl Opt, 26(1987)2938-2939.
  4. Chang C W, Su D C, An improved technique of measuring the focal length of a lens, Opt Commun, 73(1989)257-262.
  5. Su D C, Chang C W, A new technique for measuring the effective focal length of a thick or a compound lens, Opt Commun, 78(1990)118-122.
  6. Prakash O, Ram R S, Determination of focal length of convex lenses using Newton’s method, J Opt, 25(1994)135-138.
  7. Angelis M de, Nicola S De, Ferrao P, Finizio A, Pierattini G, A new approach to high accuracy measurement of the focal length of lenses using a digital Fourier transform, Opt Commun, 136(1997)370-374.
  8. Meshcheryakov V I, Sinelnikov M I, Filippov O K, Measuring the focal lengths of long-focus optical systems, J Opt Technol, 66(1999)458-459.
  9. Camacho A A, Solano C, Martinez-Ponce G, Baltazar R, Simple method to measure the focal length of lenses, Opt Eng, 41(2002)2899-2902.
  10. Boo B De, Sasián J, Novel method for precise focal length measurement, in International Optical Design Conference, 2002 OSA Technical Digest Series, (Optical Society of America, 2002), paper IMCS5.
  11. Boo B De, Sasián J, Precision focal-length measurement technique with a relative Fresnel-zone hologram, Appl Opt, 42(2003)3903-3909.
  12. Hou C, Bai J, Hou X, Novel method for testing the long focal length lens of large aperture, Opt Lasers Eng, 43 (2005)1107-1117.
  13. Bennett H E, Shaffer J J, Test facility for long focal length mirrors, Proc SPIE, 1848(2005)117-124.
  14. Chollet F, Ashraf M, Simultaneous measurement of focal length and index of refraction of a microlens using a compound microscope, J Micromech Microeng, 19(2009)1-8.
  15. Malacara-Doblado D, Salas-Peimbertc D P, Trujillo-Schiaffino G, Measuring the effective focal length and the wavefront aberrations of a lens system, Opt Eng, 49(2010)053601;
  16. Kim D -H, Shi D, Ilev I K, Alternative method for measuring effective focal length of lenses using the front and back surface reflections from a reference plate, Appl Opt, 50(2011)5163-5168.
  17. Mafusire C, Forbes A, Mean focal length of an aberrated lens, J Opt Soc Am A, 28(2011)1403-1409.
  18. Zhu X, Wu F, Cao X, Wu S, Zhang P, Jing H, Focal length measurement of microlens-array by the clarity function of digital image, Proc SPIE, 8417, (2012)84171E.
  19. Liao L, Albuquerque BFC de, Parks R E, Sasian J M, Precision focal-length measurement using imaging conjugates, Opt Eng, 51(2012)113604;
  20. Dhanotia J, Prakash S, Focal length and radius of curvature measurement using coherent gradient sensing and Fourier fringe analysis, Optik, 124 (2013)2115-2120.
  21. Pokorný P, Opat J, Mikš A, Novák J, Novák P, Analysis of factors important for measurements of focal length of optical systems. In Proceedings of the SPIE 9628, Optical Systems Design 2015: Optical Fabrication, Testing, and Metrology V, Jena, Germany, 24 September 2015. 96281Z.
  22. Ghoorchi-Beygi M, Dashtdar M, Tavassoly M T, Simple digital technique for high-accuracy measurement of focal length based on Fresnel diffraction from a phase wedge, Meas Sci Technol, 29(2018)125203.