DOCSLIB.ORG

Use of Polarising Microscope

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Use of Polarising Microscope EXPERIMENT 6 USE OF POLARISING MICROSCOPE Structure_____________________________________________________ 6.1 Introduction 6.4 Optical Properties of Minerals Expected Skills Under Plane Polarised Light 6.2 Requirements Between Cross Nicol 6.5 Laboratory Exercises 6.3 Basic Concepts Parts and Functioning of Polarising Microscope 6.6 References Adjustments of Microscope 6.7 Learning Resources 6.1 INTRODUCTION In the previous two experiments, you have identified minerals based on their physical properties. Now in the next two experiments, you would learn to identify the same minerals based on their optical properties. The optical properties are studied under the polarising/petrological microscope, using transmitted light. So, prior to that get familiarised with a polarising microscope you will be using for mineral identification. You will be handling and working on polarising microscope for the first time. In this experiment, you will learn the use of polarising microscope for the study of minerals. In this experiment we will give a brief account of polarising microscope and its functioning in the identification of minerals. You will also learn about the optical properties used for the identification of minerals both under polarised light and cross nicol condition. With the help of these optical properties you will examine and identify the minerals in the subsequent Experiments 7 and 8. Expected Skills_______________________________________________ After performing this experiment, you should be able to describe polarising microscope; discuss functioning and parts of the polarising microscope; make necessary adjustments in the microscope for its usage; list optical properties of the minerals under plane polarised light, and ……………………………..…………………….…………………………………………………………………………………………………………………………………………….BGYCL-134 Crystallography, Mineralogy and Economic Geology: Laboratory list optical properties of the minerals in cross nicol condition. 6.2 REQUIREMENTS You need to have a polarising microscope in order to know its handling and use. You will get this microscope from your study centre. If the number of microscopes is limited in the study centre, you are advised to work in groups. You would also require thin section of the mineral. Requirements Polarising microscope Mineral thin sections Instructions: You are required to study Unit 4 Polarising Microscope of BGYCT-133 course (Crystallography, Mineralogy and Economic Geology) before performing this experiment. Bring this practical manual along with Block 3 Optical Mineralogy of BGYCT-133 course while attending the Practical Counselling session. 6.3 BASIC CONCEPTS A polarising microscope, also known as petrological microscope, is a type of microscope that uses polarised and transmitted light for study of optical properties of the crystalline material such as minerals and rocks. The polarising microscopes are of two types: transmitted light microscope used for the study of rocks and minerals; and reflected light microscope used for the study of opaque minerals, mostly ores. In this experiment, we will discuss about transmitted light polarising microscope in details. 6.3.1 Parts and Functioning of Polarising Microscope A transmitted light polarising microscope is different from other microscopes as it is equipped with two polars (i.e., nicol prisms) that are oriented at right angles to each other so that their polarisation directions are perpendicular to one another (Fig. 6.1 and 6.2). The lower polarising nicol is called as the ‘polariser’ and the upper as ‘analyser’ as it aids analysis. Light source located below the stage of the microscope is initially unpolarised. It first passes through the lower polariser (usually, just called the polariser), where it gets polarised in the 94 Experiment……………………………..…………….………………………………………………………………………………………………………………………………………………… 6 Use of Polarising Microscope manner that the light starts vibrating from (the users) right to left. These directions are referred to East (right) and West (left). This is called Plane Polarised Light (abbreviated as PPL). The analyser is similar to polariser, but is oriented at right angle to polariser. It has a polarisation direction exactly perpendicular to that of the lower polariser. These directions are usually referred to North-South (Fig. 6.2a and b). Fig. 6.1: Polarising microscope and important components. When the analyser is inserted in the microscope, without a thin section of mineral specimen then the field of view becomes dark, provided polariser and analyser must be at 90º to each other. Small difference in the angle will little amount of light to pass through and field of view will not be perfectly dark. In cross nicol condition the analyser receives light vibrating in an East-West direction from the polariser, but because of orientation cannot transmit it, as it is absorbed. The above arrangement of analyser to polariser is referred to as cross polars or cross nicol condition and is abbreviated as XPL. Let us discuss different parts of the polarising microscope and their functioning. Concave mirror: Near the base of the polarising microscope, there is a concave mirror which reflects the ordinary light upwards (Fig. 6.1). The source of light may be natural like sunlight or an artificial, for example, an electric bulb. 95 ……………………………..…………………….…………………………………………………………………………………………………………………………………………….BGYCL-134 Crystallography, Mineralogy and Economic Geology: Laboratory Polariser: The ordinary light which is initially unpolarised, becomes polarised after passing through the polariser. The light leaves the polariser and starts vibrating parallel to the short diagonal of the nicol prism. This light first passes through the lower polariser (also known as polariser), where it becomes polarised and vibrates from the users right to left. These directions are referred to as East (right) and West (left). Sub-stage Diaphragm(s): One or two diaphragms may be located below the stage. Function of the diaphragms is to reduce the area of light entering the thin section. (a) (b) Fig. 6.2: Polarising Microscope: a) Parts and functioning; and b) Optical path of transmitted light. Mineral Plate on Graduated Rotating Disc or Stage: The graduated rotatable disc, on which thin section of the mineral or rock is placed, lies in between the two nicols. The microscopic stage or disc is capable of rotation and can be locked at any point. It is employed for precise angular measurement. The light entering from the polariser is resolved into two vibration directions at right angles to each another. They are parallel to the vibration direction of the mineral. Hence, two rays leave the mineral plate. Objective lens: It is placed at lower end of the microscope tube. Its function is to produce a sharp and clear image. The light passing through a hole in 96 Experiment……………………………..…………….………………………………………………………………………………………………………………………………………………… 6 Use of Polarising Microscope the rotatable stage of the microscope enters the lower lens, called an objective lens. For mineralogical work, there are three objectives: low, medium and high power for image magnification as may be required. These objectives are mounted on nose piece and can be successively rotated into position. Microscope tube: The microscope is focused by moving the tube up and down. The focusing is done by adjusting both the coarse and fine knobs. Analyser: It is the second polariser called analyser mounted within the microscope tube. It can be pushed in and out so that it can be in the light path (inserted position) or out of the light path (analyser out position or without analyser). If the analyser is out such that it is not in the light path then the polarised light is transmitted through the ocular lens. If the analyser is in, then the plane polarised light coming from the lower polariser is blocked and no light is transmitted though the ocular lens above. We have discussed this phenomenon in the earlier section. We have discussed earlier that the rays leaving the mineral plate are broken into two vibrations. One ray is parallel to the long diagonal, which is reflected out. And the other ray is parallel to the short diagonal of the analyser that reaches the eye piece. Ocular/eye piece: It is placed at the upper end of the microscope tube. The eye piece merely enlarges the image including any imperfection resulted from poor quality objective. The eye piece in the microscope contains cross- wires. Bertrand Lens: It is used to study minerals in convergent light or under conoscopic condition. It is inserted into the upper microscope tube. Condensing Lens: It is also called condenser or convergent lens. It is a small hemispherical lens attached to a bar so that it can be inserted. This lens is used when Bertrand lens is inserted. Both condensing lens and Bertrand lens are used in case of conoscopic illumination. The polarising microscope may be assembled either for orthoscopic or conoscopic illumination. The orthoscopic arrangement provides the eye with a realistic virtual image with a flat field, showing mineral thin section on the microscopic stage. If the observation is made under an orthoscopic condition, either with the polariser alone (in case of plane polarised light) or with the analyser and polariser both (in case of cross nicol) are used. If the observations are made in conoscopic arrangement, Bertrand lens and the condenser both are used. With the help of polarising microscope, it is possible to study and identify the minerals and rocks in detail. We hope that
Load more

Recommended publications
  • James Clerk Maxwell
    James Clerk Maxwell JAMES CLERK MAXWELL Perspectives on his Life and Work Edited by raymond flood mark mccartney and andrew whitaker 3 3 Great Clarendon Street, Oxford, OX2 6DP, United Kingdom Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries c Oxford University Press 2014 The moral rights of the authors have been asserted First Edition published in 2014 Impression: 1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by licence or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this work in any other form and you must impose this same condition on any acquirer Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016, United States of America British Library Cataloguing in Publication Data Data available Library of Congress Control Number: 2013942195 ISBN 978–0–19–966437–5 Printed and bound by CPI Group (UK) Ltd, Croydon, CR0 4YY Links to third party websites are provided by Oxford in good faith and for information only.
    [Show full text]
  • Polarization Phenomena of Certain Fluorites
    142 TIIE AMERICAN MINERALOGIST Pleochroic,e :colorless, ,:pale blue-green, It thus differs from the average vesuvianite only in slightly higher birefringence. The writer wishes to acknowledge his indebtedness to Col. Roebling, Mr. Gage, and Ward's Natural ScienceEstablishment for the privilege of examining specimensand to Dr. Larsen for the opticaldeterminations. POLARIZATION PHENOMENA OF CERTAIN FLUORITES A. L. PansoNs, Uniaersity oJ Toronto While determining the refractive index of fluorite by the method of minimum deviation the writer introduced a nicol prism before the telescopeof the goniometer to determine the plane of polarization of the refracted ray. On rotating the nicol no difference in the intensity of light could be observed,but on examining the reflected ray nearly complete polarization was obtained so that it was thought that the prism was not cut at the angle that should give polarization if Brewster's law applies to isometric crystals. A new prism was then cut from a crystal of fluorite from Madoc, Ontario, so that the angle between the reflected ray and the refracted ray should be ninety degrees. With this new prism the same phenomena were observed. A second nicol was now intro- duced between the collimator and the crystal so that the signal was extinguished. On rotating the two nicols simultaneously extinction was obtained throughout a complete rotation so that it would appear as though we may accept without question the state- ment that a ray of light passing through fluorite vibrates with equal facility in all directions at right angles to the direction of propagation and is not polarized.
    [Show full text]
  • GEOL 221 Mineralogy and Mineral Optics Course Syllabus
    SAN DIEGO STATE UNIVERSITY GEOL 221 Mineralogy and Mineral Optics Course Syllabus Instructor: Professor David L. Kimbrough Email: [email protected], Phone: 594-1385 Lecture: MW 1000-1050 CSL 422, Lab: W 1400-1640, Lab study: M 1400-1640 CSL 425 Office: GMCS-229A; Office hours: MW 1100-1200; T 1115-1215; by appointment TA: Mark Nahabidian GMCS-133 TBA Course Prerequisite: Chem 200 or concurrent registration. Credit or concurrent registration in OCEAN 100 or GEOL 100 and 101 or GEOL 104 and 101; Geol 200; Required Texts: Introduction to Mineralogy, William D. Nesse, Oxford University Press. Minerals in Thin Section, Perkins & Henke, Prentice Hall Recommended Text: Dictionary of Geological Terms, AGI Bates & Jackson eds. or similar, The Complete Guide to Rocks & Minerals by John Farndon or similar Other required materials: Hand lens; calculator Classroom management: Attendance is crucial. Please let me know if you’re going to be absent for any reason. Be on time for class, don’t participate in excessive side-chatter or cause disruptions during class. Always respond to the instructor, the Teaching Assistant, and your fellow students in a respectful and civil manner. Cheating or plagiarism is not tolerated. It’s easy to spot and constitutes serious academic misconduct. Helpful hints to make Mineralogy easier and more fun! Attend class: Studies show that the most valuable time commitment by students in a course is the time actually spent in the classroom. Class time is the most important determinant of student success and yields the greatest improvement in student learning outcomes. Information is covered in class that is not in the textbook, and parts of the book are hard to understand.
    [Show full text]
  • B.Sc.( Srmester-3) Subject: Physics Course: US03CPHY01 Title: Optics
    B.Sc.( Srmester-3) Subject: Physics Course: US03CPHY01 Title: Optics UNIT – III Polarization Introduction:- • Interference and diffraction phenomena proved that light is a wave motion. These phenomena are used to find wavelength of light. However, they do not give any indication regarding the character of waves. • Maxwell developed electromagnetic theory and suggested that light-waves are electromagnetic waves. Electromagnetic waves are transverse waves, so it is obvious that light waves are also transverse waves. • Longitudinal waves are waves in which particles of medium oscillate along the direction of propagation of wave (e.g. sound wave). • Transverse waves are waves in which particles of medium oscillate perpendicular to the direction of propagation of wave. (e.g. Electromagnetic waves.) • Polarization is possible in transverse wave. • Unpolarized Light is the light is which the planes of vibration are symmetrically distributed about the propagation direction of the wave. • Plane Polarized light is a wave in which the electric vector is everywhere confined to a single plane. • A linearly polarized light wave is a wave in which the electric vector oscillates in a given constant orientation. Production of Linearly Polarized Light: Linearly polarized light may be produced from unpolarized light using following optical phenomena. (i) Reflection (ii) Refraction (iii) Scattering (iv) Selective absorption (v) Double reflection. Polarized light has many important applications in industry and engineering. One of the most important applications is in liquid crystal displays (LCDs) which are widely used in wristwatches, calculators, T.V. Screens etc. An understanding of polarization is essential for understanding the propagation of electromagnetic waves guided through wave-guides and optical fibers.
    [Show full text]
  • Chapter 8 Polarization
    Phys 322 Chapter 8 Lecture 22 Polarization Reminder: Exam 2, October 22nd (see webpage) Dichroism = selective absorption of light of certain polarization Linear dichroism - selective absorption of one of the two P-state (linear) orthogonal polarizations Circular dichroism - selective absorption of L-state or R-state circular polarizations Using dichroic materials one can build a polarizer Dichroic crystals Anisotropic crystal structure: one polarization is absorbed more than the other Example: tourmaline Elastic constants for electrons may be different along two axes Polaroid 1928: dichroic sheet polarizer, J-sheet long tiny crystals of herapathite aligned in the plastic sheet Edwin Land 1938: H-sheet 1909-1991 Attach Iodine molecules to polymer molecules - molecular size iodine wires Presently produced: HN-38, HN-32, HN-22 Birefringence Elastic constants for electrons may be different along axes Resonance frequencies will be different for light polarized Refraction index depends on along different axes polarization: birefringence Dichroic crystal - absorbs one of the orthogonal P-states, transmits the other Optic axis of a crystal: the direction of linear polarization along which the resonance is different from the other two axes (assuming them equal) Calcite (CaCO3) Ca C O Image doubles Ordinary rays (o-rays) - unbent Extraordinary rays (e-rays) - bend Calcite (CaCO3) emerging rays are orthogonaly polarized Principal plane - any plane that contains optical axis Principal section - principal plane that is normal to one of the cleavage
    [Show full text]
  • Optimized Morphologic Evaluation of Biostructures by Examination in Polarized Light and Differential Interference Contrast Microscopy
    Rom J Leg Med [22] 275-282 [2014] DOI: 10.4323/rjlm.2014.275 © 2014 Romanian Society of Legal Medicine Optimized morphologic evaluation of biostructures by examination in polarized light and differential interference contrast microscopy Elena Patrascu1, Petru Razvan Melinte1, Gheorghe S. Dragoi2,* _________________________________________________________________________________________ Abstract: Differential interference contrast microscopy (DIC) was possible after the invention of Wollaston prisms that were modified by Nomarski and could duplicate linear polarized light before passing through a specimen (Condenser DIC prism) and to recompose it afterwards (Objective DIC prism), thus creating the phenomenon of interference that depends on the thickness and birefringence of the studied structures. The authors proposed themselves to discuss the performances of this microscope and to widen the area of its usage in the optimized microanatomic analysis of cells and tissues on the native or stained sections. The authors consider it necessary to use DIC microscopy both in forensic medicine (identification of diatoms) as well as in reproduction biology (spermogram) and in early discovery of uterine cervix cancer. Key Words: DIC microscopy, Wollaston prism, Nomarski prism, polarized light, interference. he progresses achieved in the area of wave (Maxwell, 1864) [2] and has a photogenic improvement and diversification of structure (Einstein, 1921) [3]. It consists of an electric T optic systems determined the increase of photonic and a magnetic field, orthogonal, which vibrate in microscopes performances regarding the phase contrast, phase, in the direction of propagation. Within an polarized light and not least, differential interference electromagnetic wave, the electric and the magnetic contrast (DIC) examinations.They assure nowadays fields oscillate simultaneously, but in different planes.
    [Show full text]
  • Optic Axis of a Crystal: the Direction of Linear Polarization Along Which the Resonance Is Different from the Other Two Axes (Assuming Them Equal) Calcite (Caco3)
    Phys 322 Chapter 8 Lecture 22 Polarization Dichroism = selective absorption of light of certain polarization Linear dichroism - selective absorption of one of the two P-state (linear) orthogonal polarizations Circular dichroism - selective absorption of L-state or R-state circular polarizations Using dichroic materials one can build a polarizer Dichroic crystals Anisotropic crystal structure: one polarization is absorbed more than the other Example: tourmaline Elastic constants for electrons may be different along two axes Polaroid 1928: dichroic sheet polarizer, J-sheet long tiny crystals of herapathite aligned in the plastic sheet Edwin Land 1938: H-sheet 1909-1991 Attach Iodine molecules to polymer molecules - molecular size iodine wires Presently produced: HN-38, HN-32, HN-22 Birefringence Elastic constants for electrons may be different along axes Resonance frequencies will be different for light polarized Refraction index depends on along different axes polarization: birefringence Dichroic crystal - absorbs one of the orthogonal P-states, transmits the other Optic axis of a crystal: the direction of linear polarization along which the resonance is different from the other two axes (assuming them equal) Calcite (CaCO3) Ca C O Image doubles Ordinary rays (o-rays) - unbent Extraordinary rays (e-rays) - bend Calcite (CaCO3) emerging rays are orthogonaly polarized Principal plane - any plane that contains optical axis Principal section - principal plane that is normal to one of the cleavage surfaces Birefringence and Huygens’ principle
    [Show full text]
  • The Role of the Petrographic Microscope in Criminal Investigations George T
    Journal of Criminal Law and Criminology Volume 31 Article 12 Issue 2 July-August Summer 1940 The Role of the Petrographic Microscope in Criminal Investigations George T. Faust Follow this and additional works at: https://scholarlycommons.law.northwestern.edu/jclc Part of the Criminal Law Commons, Criminology Commons, and the Criminology and Criminal Justice Commons Recommended Citation George T. Faust, The Role of the Petrographic Microscope in Criminal Investigations, 31 Am. Inst. Crim. L. & Criminology 246 (1940-1941) This Criminology is brought to you for free and open access by Northwestern University School of Law Scholarly Commons. It has been accepted for inclusion in Journal of Criminal Law and Criminology by an authorized editor of Northwestern University School of Law Scholarly Commons. THE ROLE OF THE PETROGRAPHIC MICROSCOPE IN CRIMINAL INVESTIGATIONS George T. Fust* There are many instances when it is objective. The purpose of the lower not possible to completely solve prob- one is to plane polarize the light which lems involving the analysis of sub- passes through the microscope. 2 The stances by either chemical or spectro- second prism, in combination with the graphic means. In such cases the de- polarizer, is utilized to determine the termination of the index of refraction optical properties of the crystal being and other optical properties by means studied.' of the petrographic microscope may While the applications of the petro- prove of value. (The index of refrac- graphic microscope are extensive, prob- tion is an optical property character- ably its most frequent use is found in istic of any particular crystalline sub- studies of the refractive index of glass stance, and it is measured by the ve- fragments picked up at crime scenes, locity with which light is transmitted and of abrasives which have been used through that substance, as compared in sabotage cases.
    [Show full text]
  • How to Generate Polarized Light?
    Before this lecture there were two lectures: 1. Qualitative description of polarization and generation of various polarized light. 2. Quantitative derivation and explaining the observations. 08/08/2017 How to generate Polarized Light? 1.Dichroic materials 2.Polarizer 3.Birefringent materials 4.Reflection 5.Scattering Wire grid polarizer Birefringence Polarized Reflecting Light • When an unpolarized light wave reflects off a non-metallic surface, it can be completely polarized, partially polarized or unpolarized depending on the angle of incidence. A completely polarized wave occurs for an angle called Brewster’s angle (named after Sir David Brewster) Snell's law Incident Reflected ray ray p n 90o 1 n2 r n1sin P = n2sin r n1sin P = n2sin r = n2sin (90-P) = n2cos P tan P = n2/n1 P = Brewster’s angel Reflection • When an unpolarized wave reflects off a nonmetallic surface, the reflected wave is partially plane polarized parallel to the surface. The amount of polarization depends upon the angle (more later). The reflected ray contains more vibrations parallel to the reflecting surface while the transmitted beam contains more vibrations at right angles to these. Applications • Knowing that reflected light or glare from surfaces is at least partially plane polarized, one can use Polaroid sunglasses. The polarization axes of the lenses are vertical as the glare usually comes from reflection off horizontal surfaces. Polarized Lens on a Camera Reduce Reflections Polarization by Scattering • When a light wave passes through a gas, it will be absorbed and then re-radiated in a variety of directions. This process is called scattering. y Gas molecule z O Unpolarized x sunlight Light scattered at right angles is plane-polarized Polarization by Scatterings Retarders • In retarders, one polarization gets ‘retarded’, or delayed, with respect to the other one.
    [Show full text]
  • Polarisation
    Polarisation In plane polarised light, the plane containing the direction of POLARISATION vibration and propagation of light is called plane of vibration. Polarisation Plane which is perpendicular to the plane of vibration is called plane of polarisation. The phenomenon due to which vibrations of light waves are restricted in a particular plane is called polarisation. In an ordinary beam of light from a source, the vibrations occur normal to the direction of propagation in all possible planes. Such beam of light called unpolarised light. If by some methods (reflection, refraction or scattering) a beam of light is produced in which vibrations are confined to only one plane, then it is called as plane polarised light. Hence, polarisation is the phenomenon of producing plane polarised light from unpolarised light. In above diagram plane ABCD represents the plane of vibration and EFGH represents the plane of polarisation. There are three type of polarized light 1) Plane Polarized Light 2) Circularly Polarized Light 3) Elliptically Polarized Light Page 1 of 12 Prof. A. P. Manage DMSM’s Bhaurao Kakatkar College, Belgaum Polarisation Huygen’s theory of double refraction According to Huygen’s theory, a point in a doubly refracting or birefringent crystal produces 2 types of wavefronts. The wavefront corresponding to the O-ray is spherical wavefront. The ordinary wave travels with same velocity in all directions and so the corresponding wavefront is spherical. The wavefront corresponding to the E-ray is ellipsoidal wavefront. Extraordinary waves have different velocities in Polarised light can be produced by either reflection, different directions, so the corresponding wavefront is elliptical.
    [Show full text]
  • PME557 Engineering Optics
    PME557 Engineering Optics Wei-Chih Wang National Tsinghua University Department of Power Mechanical Engineering 1 W.Wang Class Information • Time: Lecture M 1:20-3:10 (Eng Bldg 1 211) Lab Th 1:10-2:10 PM (TBA) • Instructor: Wei-Chih Wang office: Delta 319 course website: http://depts.washington.edu/mictech/optics/me557.index.html • Suggested Textbooks: - Optical Methods of Engineering Analysis, Gary Cloud, Cambridge University Press. - Handbook on Experimental Mechanics, Albert S. Kobayashi, society of experimental mechanics. - Applied Electromagnetism, Liang Chi Shen, Weber&Schmidt Dubury - Fundamentals of Photonics, B. Saleh, John Wiley& Sons. - Optoelectronics and Photonics: Principles and Practices, S. O. Kasap, Prentice Hall. - Fiber optic Sensors, E. Udd, John Wiley& Sons - Selected papers in photonics, optical sensors, optical MEMS devices and integrated optical devices. 2 W.Wang Class information • Grading Homework and Lab assignments 80% (3 assignments and 3 lab reports) Final Project 20% • Final Project: - Choose topics related to simpleo free space optics design, fiberopic sensors, waveguide sensors or geometric Moiré, Moiré interferometer, photoelasticity for mechanical sensing or simple optical design. - Details of the project will be announced in mid quarter - Four people can work as a team on a project, but each person needs to turn in his/her own final report. - Oral presentation will be held in the end of the quarter on your final project along with a final report. 3 W.Wang Objectives The main goal of this course is to
    [Show full text]
  • Polarization Imaging: Principles and Integrated Polarimeters Andreas G
    566 IEEE SENSORS JOURNAL, VOL. 2, NO. 6, DECEMBER 2002 Polarization Imaging: Principles and Integrated Polarimeters Andreas G. Andreou and Zaven Kevork Kalayjian Abstract—Polarization is a general descriptor of light and con- of Huygens, Young, Fresnel, and Maxwell to lead us to the tains information about reflecting objects that traditional inten- understanding of the polarization of light that we have today; sity-based sensors ignore. Difficult computer vision tasks such as and, its study has lead to a deeper understanding of light and image segmentation and object orientation are made tractable with polarization vision techniques. Specularities, occluding contours, light-matter interaction. and material properties can be readily extracted if the Stokes po- Polarization is used to classify chemical isomers [22], to an- larization parameters are available. Astrophysicists employ polar- alyze solar and atmospheric phenomena [23], [24], to investi- ization information to measure the spatial distribution of magnetic gate stress and strain through photoelasticity, to classify mate- fields on the surface of the sun. In the medical field, analysis of the rials and recognize objects [25]–[30], and to analyze reflections polarization allows the diagnose of disease in the eyes. The retinae of most insect and certain vertebrate species are sensitive to polar- [31], [32]. Polarimetric devices and techniques have been in- ization in their environment, but humans are blind to this prop- vented to filter, separate, quantify, and modulate polarized light. erty of light. Biologists use polarimeters to investigate behaviors of Polaroid filters are used in magneto-optic drives, liquid crystal animals—vis-à-vis polarization—in their natural habitats.
    [Show full text]