DIFFRACTIVE OPTICAL ELEMENTS IN SPECKLE METROLOGY AND TEMPERATURE MEASUREMENT

Transcription

1 DIFFRACTIVE OPTICAL ELEMENTS IN SPECKLE METROLOGY AND TEMPERATURE MEASUREMENT By A. J. PRAMILA DANIEL Instrument Design Development Centre THESIS SUBMITTED IN FULFILMENT OF THE REQUIREMENTS OF THE DEGREE OF DOCTOR OF PHILOSOPHY to the INDIAN INSTITUTE OF TECHNOLOGY, DELHI INDIA JUNE, 1993

2 Dedicated to my dear father and the loving memory of my mother

3 CERTIFICATE This is to certify that the thesis entitled, "DIFFRACTIVE OPTICAL ELEMENTS IN SPECKLE METROLOGY AND TEMPERATURE MEASUREMENT', being submitted by Ms. A.J. Pramila Daniel, to the Indian Institute of Technology, Delhi, for the award of the degree of " DOCTOR OF PHILOSOPHY ", is a record of the bonafide research work carried out by her under my supervision and guidance. She has fulfilled the requirements for submission of this thesis, which to the best of my knowledge, has reached the required standard. The material contained in this thesis has not been submitted in part or full to any other University or Institute for the award of any degree or diploma. Dr. Chandra Shakher Chief Design Engineer Instrument Design Development Centre I.I.T. Delhi

4 ACKNOWLEDGEMENT First and foremost I would like to thank God, the Almighty for his immeasurable help at every stage of my work. It is my pleasant duty to place on record, my deep indebtedness to Dr. Chandra Shakher. I wish to express my heartfelt gratitude to him, for his constant encouragement and his unbounded patience. Dr. Chandra Shakher has, on several occasions, put in hours of hard work to sort out intractable problems. Without his excellent insight into the topic and but for his continued guidance, the work being reported upon in this thesis, would not have been completed in such a short time. It is my bounden duty to record the inspiration and encouragement received from all the faculty of I.D.D.C. I am especially grateful to Dr. Rakesh Kumar, Head, I.D.D.C., for permitting me to use the facilities available in his laboratory. My heartfelt gratitude to Prof. Robin Smith and Lt. K.Suresh for their valuable discussions and help rendered in solving the Abel integral equation and other mathematical problems. I am grateful to Mr.D.Ravi for making use of the sygraph to draw the pseudo colour maps for temperature profile. I am thankful for the moral support and kind help rendered by Ms. Anu Sharma. I am also thankful to Ms.Pushpa Jha for her continual support and help. I wish to acknowledge the ceaseless encouragement and excellent cooperation received from my colleagues Dr. H.L. Yadav, Mr. A.K. Nirala, Mr. R. Sankara Kumar, Ms. Sharmila, Mr, Manoj. Mr.S.K.Verma and Mr.Shashi Prakash.

5 I am extremely grateful to Mr. R.B. Verma for his personal cooperation and the technical support rendered by him. I am also thankful to Mr. G.R.Mehta, Mr. H.S. Sharma and Mr.Hoshiar Singh for their cooperation and technical support. My thanks are due to all the staff of the Optics laboratory and the Workshop. I am grateful to Mr. Prabhunath for his excellent cooperation and his drawings, to Mr. Bhatia for his photographs of the experimental setups and Mr.Dixit for his cooperation. I wish to express my heart felt gratitude to my parents, husband and family members for their constant encouragement, immeasurable patience and support. My special thanks are due to my brother, Dr. Joseph Daniel and his family for all the support and encouragement without which my stay in Delhi would have become quite difficult. My sincere thanks to Mr. A.R.Fraser for his help in the library work and inspiration. Date : A T. Za (A.J. Pramila Daniel)

6 ABSTRACT In recent years, there is an increasing interest in the optical elements which work on the phenomenon of light diffraction. These elements are called diffractive optical elements (DOEs). In a number of specific applications DOES either cannot be replaced by conventional elements which work on the traditional phenomenon of refraction or have great advantages over them. They are light weight, cheap and can be easily replicated. Further, the time needed to manufacture them is much shorter than that needed for conventional glass elements. The DOEs can be constructed either by optical holography or by computerized designs. A large variety of fabrication techniques have been used for the production of computer generated holograms. Large number of uses of DOEs as elements of head up displays, fibre optical couplers, solar concentrators, white light imaging systems, imaging systems for speckle metrology have been successfully demonstrated. Diffracting grids are also used in Moire deflectometry, Talbot interferometry etc. In this thesis, the use of diffractive optical elements (compact hololens system imaging) in speckle metrology and ( speckle photography and diffractive grids) in temperature measurement of gaseous flames is investigated. Chapter I provides a brief introduction to diffractive optical elements, holographic lenses and their use in speckle metrology, compact hololens imaging systems, Talbot effect with Moire read out, flames and optics of flames. Chapter II deals with the imaging properties of two element compact hololens imaging system and its use in the measurement of in-plane translation and rotation using speckle photography and speckle interferometry. Lens recording, play back geometry for the compact hololens imaging system is also given.

7 Chapter III presents the determination of temperature distribution of axisymmetric gaseous flames using speckle photography. The optimisation of the experimental parameters to get temperature over the entire volume of the flame is given. Chapter IV deals with the determination of temperature distribution in axisymmetric gaseous flames using Talbot interferometry. The Talbot interferometer with circular gratings is optimised to enhance the sensitivity. Under this conditions, fringes are obtained with good contrast also. The experiment is conducted and mathematical modelling is done to calculate the angle of refraction and thereby to calculate the temperature. The temperature distribution of a bunsen burner flame is determined. Chapter V gives the details of the experiment and the mathematical modelling to determine the temperature profile of a 2-dimensional slot burner taken from atomic absorption spectrophotometer. The error analysis for temperature calculation is also included. The investigations presented in this thesis reveal that diffractive optical elements can be advantageously employed in speckle metrology and temperature measurement. Further, since these are light weight, cheap and can be easily replicated, they are viable alternatives to conventional optical elements in many specific applications.

8 THE WORK HAS RESULTED IN THE FOLLOWING PUBLICATIONS : PUBLICATIONS IN JOURNALS : 1. Chandra Shakher, A.K.Nirala, Joan Pramila, S.K.Verma, " Use of speckle technique for temperature measurement in gaseous flames ", -J.Optics (Paris) Vol. 23, No.2, pp A.J.Pramila Daniel, Shashi Prakash and Chandra Shakher, " Compact hololens imaging system in speckle photography and speckle interferometry ", Optik Vol.93, No.1, (1993). 3. Chandra Shakher, A.J.Pramila Daniel, " Talbot interferometer with circular gratings for the measurement of temperature in axisymmetric gaseous flames ", - Applied Optics (Communicated). 4. Chandra Shakher, A.J.Pramila Daniel, "Measurement of temperature profile of atomic absorption spectrophotometer burner. (Premixed laminar flow slot-burner) using Talbot interferometer"- Communicated to Optical Engineering PUBLICATIONS IN NATIONAL/INTERNATIONAL CONFERENCES 5. C.Shakher, H.L.Yadav, A.J.Pramila Daniel, " Sub micron speckle metrology using hololenses ", - 6 th International Precision Engineering Seminar, May, 1991, Braunschweig, FRG. 6. C.Shakher, H.L.Yadav, A.J.Pramila Daniel "Design analysis and realisation of hololens imaging system for speckle metrology 'Third International Conference on "Holographic systems components and applications", 16-18, September 1991 in U.K.

9 7. C.Shakher, A.K.Nirala, Joan Pramila, S.K.Verma, "Use of speckle technique for temperature measurement in gaseous flames ",- 19 th OSI Symposium on optics and National Development, Lucknow 8-10 March, 1991.

10 CONTENTS CHAPTER I Introduction Diffractive Optical Elements Compact Two-Hololens System Imaging in Speckle Metrology Speckle Metrology Objective Speckle Pattern Subjective Speckle Pattern Speckle Photography Measurement of In-plane Translation 11 Using Double Exposure Image Plane Speckle Photography Method of Analysing Doubly Exposed Specklegram 11 Pointwise Filtering Method Correction for the Errors in the Measurement 13 of Fringe Spacing of the Young's Fringes in case of Pointwise Filtering of Doubly Exposed Specklegrams Speckle Interferometry Flames Optics of Flames Talbot Effect and Moire Read Out 20

11 CHAPTER II Compact Hololens Imaging System in Speckle Photography and Speckle Interferometry 2.1 Introduction Speckle Photography Lens Recording and Playback Geometry Experimental Data Analysis Results and Discussions Speckle Interferometry Experimental Setup for Measurement of In-Plane 45 Displacement and In-Plane Rotation Results and Discussions Conclusions 48 CHAPTER III Temperature Measurement in Axi-Symmetric Gaseous Flames using Speckle Photography 3.1 Introduction Theory Experimental Optimisation of Experimental Parameters Discussions and Conclusions 70

12 CHAPTER IV Temperature Measurement in Axi Symmetric Gaseous Flames Using Talbot Interferometry 4.1 Introduction Talbot Effect Theory Optimisation of Experimental Parameters Experimental Discussions 85 CHAPTER V Temperature Profile Measurement of Atomic Absorption Spectrophotometer Burner (Pre- Mixed Laminar Flow Slot-Burner) Using Talbot Interferometer 5.1 Introduction Theory Experimental Setup Error Analysis Results Discussions and Conclusions 113 References 115 Appendix 129 Author's Biography 132,