Switchable Retroreflector Films for Enhanced Visible and Infrared Conspicuity

Total Page:16

File Type:pdf, Size:1020Kb

Switchable Retroreflector Films for Enhanced Visible and Infrared Conspicuity Switchable Retroreflector Films for Enhanced Visible and Infrared Conspicuity: Naked eye response switchable retroreflectors with integration into an optical interrogation and response system A dissertation submitted to the Division of Research and Advanced Studies of the University of Cincinnati in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY (Ph.D.) In the Department of Electronic and Computing Systems of the College of Engineering and Applied Science 2015 by Phillip Jordan Schultz B.S., University of Cincinnati, 2009 Dr. Jason C. Heikenfeld, Committee Chair Abstract Retroreflectors are common optical devices used in several commercial conspicuity applications. Since the 1980's, there have been several investigations aimed at switching the retroreflected signal. Most of the developed switching technologies are based on MEMS actuation and quantum mechanics, among others. These devices were aimed at the free-space optical communications markets, lending them to have high operating speeds. However, they are limited by single devices/small areas, spectral range (short wave infrared), low contrast, physical rigidity, and high fabrication costs. For naked eye conspicuity applications, these limitations are not suitable. The approach presented in this dissertation does not provide the high switching speeds of the previous MEMS and MQW methods, but provides superior performance in nearly all other metrics of interest to visual conspicuity applications, most notably safety. These metrics include high contrast of >2000:1 at 635 nm, and >400:1 at 850 nm, large area of 75 cm2 +, visible and infrared operational spectral range from 400 - 1600 nm, input angles of ±38o, optical efficiencies of 25%, low power, thin and flexible construction at <0.6 mm thick, and switching speeds sufficient for rapid visualization (<100 ms). This dissertation investigates several novel types of switchable retroreflectors, and compares them to a set of desired metrics for naked eye applications. It determines that the use of a polymer dispersed liquid crystal (PDLC) based switchable retroreflector would be the ideal choice for such applications. This dissertation further achieves a complete system level integration and demonstration, including development of an encoded laser interrogation system. It provides optical models for both day and night operation. It also provides day and night field demonstration results using visible (2.5 - i 10 mW - 635nm) and infrared (1.5 mW - 850 nm) light sources (with night vision) out to 400 meters to validate the technology’s viability and potential use. Overall, the goal of this dissertation is to introduce and demonstrate an improved switchable retroreflector and electronic system satisfying all of the ideal requirements for enhanced naked-eye optical conspicuity. ii Copyright Page iii Acknowledgements I would not have been able to complete, much less pursue, this dissertation without the help and support of several individuals throughout my personal and professional life. I would like to thank some of them here. First, I would like to thank some of those closest to me. I would like to thank my wonderful wife, Carrie, for being there when I needed her on several levels. Though there were ups, and downs, she hung in there and allowed me to finish without worries. I would like to thank my son, Sullivan, for always being there and putting a smile on my face when I needed it most. Next, I would like to thank my parents for emphasizing the importance of education and doing everything to the best of your ability. I would also like to thank my twin brother, Alex, for always giving me that on-the-spot competition that you cannot find anywhere else. I would like to thank my advisor and mentor, Dr. Jason Heikenfeld. His support, and seemingly non-human levels of energy, helped push me to work harder to achieve what I wanted on a daily basis. His advice, encouragement, and guidance, allowed me to complete this dissertation knowing I would be proud of the work I had accomplished. I would also like to thank all of my committee members for their encouragement and acceptance throughout my Ph.D. candidacy. I would like to thank my financial, material, and equipment support from , Xetron, and Reflexite. Without their help, none of this would have been possible. I would also like to thank everyone from NDL. Their encouragement, friendship, training, and assistance, helped get me through the occasional grind and allowed me to understand what a cohesive work environment can do. I would especially like to thank iv Brad Cumby, who took time out of his day to help me collect data for my various field demonstrations. Life would have been a lot more difficult without that. I still owe him. I would finally like to thank all of the faculty and staff of the University of Cincinnati. Their assistance, support, and guidance allowed me to pursue my aspirations for the last 9+ years with relative ease. I am proud of my undergraduate and graduate tenure here. I will encourage others to follow the same path. v Table of Contents Abstract .......................................................................................................................... i Copyright Page ............................................................................................................. iii Acknowledgements ...................................................................................................... iv Table of Contents ......................................................................................................... vi List of Figures .............................................................................................................. xi List of Tables .............................................................................................................. xiv Chapter 1: Introduction ................................................................................................. 1 1.1 Introduction to this Chapter ............................................................................... 1 1.2 Conspicuity ....................................................................................................... 1 1.3 Retroreflectors: Theory in Brief ......................................................................... 2 1.4 Research Aims and Outline ............................................................................... 5 1.5 References........................................................................................................ 7 Chapter 2: Background and Prior Art ......................................................................... 8 2.1 Introduction ....................................................................................................... 8 2.2 Prior Art ............................................................................................................. 8 2.2.1 Micro-Electro-Mechanical Systems (MEMS) Retroreflectors ........................... 9 2.2.2 Multiple Quantum Well (MQW) Retroreflector ............................................... 13 2.3 Display Technologies ...................................................................................... 16 2.3.1 Electrowetting ............................................................................................... 16 2.3.2 Liquid Crystal ............................................................................................... 19 vi 2.4 Summary ........................................................................................................ 23 2.5 References...................................................................................................... 24 Chapter 3 - Comparison of 5 Types of Switchable Retroreflectors ......................... 29 3.1 Introduction ..................................................................................................... 29 3.2 Background ..................................................................................................... 29 3.3 Choosing the Retroreflecting Optical Film ....................................................... 30 3.4 Selection of Electrical Modulation Methods ..................................................... 33 3.4.1 Electrowetting ............................................................................................... 34 3.4.2 Liquid Crystal ............................................................................................... 34 3.5 Optical Efficiency Model .................................................................................. 35 3.6 Electrowetting Lenslet Scattering .................................................................... 36 3.6.1 Fabrication and Construction ........................................................................ 36 3.6.2 Electrical Switching ...................................................................................... 36 3.6.3 Retroreflection Results ................................................................................. 38 3.6.4 Discussion .................................................................................................... 39 3.7 External Electrowetting Light Valve ................................................................. 40 3.7.1 Fabrication and Construction ........................................................................ 40 3.7.2 Electrical Switching ...................................................................................... 40 3.7.3 Preliminary Results .....................................................................................
Recommended publications
  • The Diffuse Reflecting Power of Various Substances 1
    . THE DIFFUSE REFLECTING POWER OF VARIOUS SUBSTANCES 1 By W. W. Coblentz CONTENTS Page I. Introduction . 283 II. Summary of previous investigations 288 III. Apparatus and methods 291 1 The thermopile 292 2. The hemispherical mirror 292 3. The optical system 294 4. Regions of the spectrum examined 297 '. 5. Corrections to observations 298 IV. Reflecting power of lampblack 301 V. Reflecting power of platinum black 305 VI. Reflecting power of green leaves 308 VII. Reflecting power of pigments 311 VIII. Reflecting power of miscellaneous substances 313 IX. Selective reflection and emission of white paints 315 X. Summary 318 Note I. —Variation of the specular reflecting power of silver with angle 319 of incidence I. INTRODUCTION In all radiometric work involving the measurement of radiant energy in absolute value it is necessary to use an instrument that intercepts or absorbs all the incident radiations; or if that is impracticable, it is necessary to know the amount that is not absorbed. The instruments used for intercepting and absorbing radiant energy are usually constructed in the form of conical- shaped cavities which are blackened with lampblack, the expecta- tion being that, after successive reflections within the cavity, the amount of energy lost by passing out through the opening is reduced to a negligible value. 1 This title is used in order to distinguish the reflection of matte surfaces from the (regular) reflection of polished surfaces. The paper gives also data on the specular reflection of polished silver for different angles of incidence, but it seemed unnecessary to include it in the title.
    [Show full text]
  • How Can Retroreflective Clothing Provide More Safety Through Visibility in a Semi-Dark Urban Environment? a Study Taking Plac
    MASTER’S THESIS How can retroreflective clothing BY VIOLA SCHMITZ provide more safety through visibility in a semi-dark urban Royal Institute of Technology environment? KTH School of Architecture Master’s Program in A study taking place in Scandinavia. Architectural Lighting Design 2018-2019 24.05.2019 AF270X VT19-1 Tutor: Foteini Kyriakidou 0 Index Abstract P. 2 1. Introduction P. 2 2. Background P. 3 2.1. Urban Background P. 4 2.2. Biological background P. 4 2.2.1. Reflexes and reactions P. 4 2.2.2. Types of vision P. 4 2.2.3. Effect of pattern P. 5 recognition 2.2.4. Human field of vision P. 5 3. Analysis P. 6 3.1. Analysis: Retroreflectors P. 6 3.2. Analysis: Existing products P. 7 4. Methodology P. 9 5. Methods P. 10 5.1. Survey: P. 10 Lines defining the human body 5.2. Video Experiment: P. 10 Designs in motion 5.2.1. Analysis: Location P. 10 5.2.2. Video Experiment P. 11 5.2.3. Procedure P. 12 5.3. Experimental survey: P. 12 Size of a human 5.4. Visualization: P. 13 Pattern recognition in surroundings 6. Results P. 14 6.1. Survey: P. 14 Lines defining the human body 6.2. Video Experiment: P. 15 Designs in motion 6.2.1. Analysis: Location P. 15 6.2.2. Video Experiment P. 16 6.2.3. Observation P. 17 6.3. Experimental survey: P. 17 Size of a human 6.4. Visualization: Pattern P. 17 recognition in surroundings 7. Discussion P.
    [Show full text]
  • Some Diffuse Reflection Problems in Radiation Aerodynamics Stephen Nathaniel Falken Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1964 Some diffuse reflection problems in radiation aerodynamics Stephen Nathaniel Falken Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Aerospace Engineering Commons Recommended Citation Falken, Stephen Nathaniel, "Some diffuse reflection problems in radiation aerodynamics " (1964). Retrospective Theses and Dissertations. 3848. https://lib.dr.iastate.edu/rtd/3848 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been 65-4604 microfilmed exactly as received FALiKEN, Stephen Nathaniel, 1937- SOME DIFFUSE REFLECTION PROBLEMS IN RADIATION AERODYNAMICS. Iowa State University of Science and Technology Ph.D., 1964 Engineering, aeronautical University Microfilms, Inc., Ann Arbor, Michigan SOME DIFFUSE REFLECTIOU PROBLEMS IN RADIATION AERODYNAMICS "by Stephen Nathaniel Falken A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF HîILOSOEHï Major Subjects: Aerospace Engineering Mathematics Approved: Signature was redacted for privacy. Cmrg^Vf Major Work Signature was redacted for privacy. Heads of Mgjor Departments Signature was redacted for privacy. De of Gradu^ e College Iowa State University Of Science and Technology Ames, loTfa 196k ii TABLE OF CONTENTS page DEDICATION iii I. LIST OF SYMBOLS 1 II. INTRODUCTION. 5 HI. GENERAL AERODYNAMIC FORCE ANALYSIS 11 IV. THE THEORY OF RADIATION AERODYNAMICS Ik A.
    [Show full text]
  • Ap Physics 2 Summary Chapter 21 – Reflection and Refraction
    AP PHYSICS 2 SUMMARY CHAPTER 21 – REFLECTION AND REFRACTION . Light sources and light rays Light Bulbs, candles, and the Sun are examples of extended sources that emit light. Light from such sources illuminates other objects, which reflect the light. We see an object because incident light reflects off of it and reaches our eyes. We represent the travel of light rays (drawn as lines and arrows). Each point of a shining object or a reflecting object send rays in all directions. Law of reflection When a ray strikes a smooth surface such as a mirror, the angle between the incident ray and the normal line perpendicular to the surface equals the angle between the reflected ray and the normal line (the angle of incidence equals the angle of reflection). This phenomenon is called specular reflection. Diffuse reflection If light is incident on an irregular surface, the incident light is reflected in many different directions. This phenomenon is called diffuse reflection. Refraction If the direction of travel of light changes as it moves from one medium to another, the light is said to refract (bend) as it moves between the media. Snell’s law Light going from a lower to a higher index of refraction will bend toward the normal, but going from a higher to a lower index of refraction it will bend away from the normal. Total internal reflection If light tries to move from a more optically dense medium 1 of refractive index n1 into a less optically dense medium 2 of refractive index n2 (n1>n2), the refracted light in medium 2 bends away from the normal line.
    [Show full text]
  • Method for Measuring Solar Reflectance of Retroreflective Materials Using Emitting-Receiving Optical Fiber
    Method for Measuring Solar Reflectance of Retroreflective Materials Using Emitting-Receiving Optical Fiber HiroyukiIyota*, HidekiSakai, Kazuo Emura, orio Igawa, Hideya Shimada and obuya ishimura, Osaka City University Osaka, Japan *Corresponding author email: [email protected] ABSTRACT The heat generated by reflected sunlight from buildings to surrounding structures or pedestrians can be reduced by using retroreflective materials as building exteriors. However, it is very difficult to evaluate the solar reflective performance of retroreflective materials because retroreflective lightcannotbe determined directly using the integrating sphere measurement. To solve this difficulty, we proposed a simple method for retroreflectance measurementthatcan be used practically. A prototype of a specialapparatus was manufactured; this apparatus contains an emitting-receiving optical fiber and spectrometers for both the visible and the infrared bands. The retroreflectances of several types of retroreflective materials are measured using this apparatus. The measured values correlate well with the retroreflectances obtained by an accurate (but tedious) measurement. The characteristics of several types of retroreflective sheets are investigated. Introduction Among the various reflective characteristics, retroreflective materials as shown in Fig.1(c) have been widely used in road signs or work clothes to improve nighttime visibility. Retroreflection was given by some mechanisms:prisms, glass beads, and so on. The reflective performance has been evaluated from the viewpointof these usages only. On the other hand, we have shown thatretroreflective materials reduce the heatgenerated by reflected sunlight(Sakai, in submission). The use of such materials on building exteriors may help reduce the urban heatisland effect. However, itis difficultto evaluate the solar reflective performance of retroreflective materials because retroreflectance cannot be determined using Figure 1.
    [Show full text]
  • Reflection Measurements in IR Spectroscopy Author: Richard Spragg Perkinelmer, Inc
    TECHNICAL NOTE Reflection Measurements in IR Spectroscopy Author: Richard Spragg PerkinElmer, Inc. Seer Green, UK Reflection spectra Most materials absorb infrared radiation very strongly. As a result samples have to be prepared as thin films or diluted in non- absorbing matrices in order to measure their spectra in transmission. There is no such limitation on measuring spectra by reflection, so that this is a more versatile way to obtain spectroscopic information. However reflection spectra often look quite different from transmission spectra of the same material. Here we look at the nature of reflection spectra and see when they are likely to provide useful information. This discussion considers only methods for obtaining so-called external reflection spectra not ATR techniques. The nature of reflection spectra The absorption spectrum can be calculated from the measured reflection spectrum by a mathematical operation called the Kramers-Kronig transformation. This is provided in most data manipulation packages used with FTIR spectrometers. Below is a comparison between the absorption spectrum of polymethylmethacrylate obtained by Kramers-Kronig transformation of the reflection spectrum and the transmission spectrum of a thin film. Figure 1. Reflection and transmission at a plane surface Reflection takes place at surfaces. When radiation strikes a surface it may be reflected, transmitted or absorbed. The relative amounts of reflection and transmission are determined by the refractive indices of the two media and the angle of incidence. In the common case of radiation in air striking the surface of a non-absorbing medium with refractive index n at normal incidence the reflection is given by (n-1)2/(n+1)2.
    [Show full text]
  • Birdshot Chorioretinopathy
    Ocular Inflammation Service, Oxford Eye Hospital Birdshot Chorioretinopathy Information for patients What is birdshot chorioretinopathy? Birdshot chorioretinopathy (or retinochoroidopathy), normally shortened to ‘birdshot’, is a rare, potentially blinding, posterior uveitis. This is chronic inflammation of the choroid, which also tends to affect the retina and retinal vessels. It affects both eyes. In the picture below, you can see the position of the vitreous, retina and uvea (iris, ciliary body, pars planar and choroid), which has three sections; anterior, intermediate and posterior. The dotted area represents the uvea. Choroid Retina Vitreous Cornea Macula Lens Fovea Iris Optic nerve Ciliary body anterior intermediate posterior page 2 Birdshot chorioretinopathy is characterised by inflammation of the vitreous (clear jelly in the eye) which causes orange, yellow or cream coloured oval shaped spots at the back of your eye on your retina. These affect the macula (an area near the centre of the retina used for detailed vision) and can cause vision loss. The reason this disease is called ‘birdshot’ is because these spots look like the pattern seen when you fire birdshot pellets from a shotgun. What causes birdshot? It is believed to be due to an autoimmune disease. An autoimmune disease is an illness that occurs when the body tissues are attacked by its own immune system, which causes chronic inflammation. It is most likely to develop in people aged between 45 and 55, although it can also occur in much younger and older people. Birdshot is a relatively new disease. It was first discovered in 1949 and only given the title ‘birdshot’ in 1980.
    [Show full text]
  • Next-Generation Laser Retroreflectors for Precision Tests of General
    UNIVERSITA` DEGLI STUDI “ROMA TRE” DOTTORATO DI RICERCA IN FISICA XXVIII CICLO Next-generation Laser Retroreflectors for Precision Tests of General Relativity Relazione sull’attivit`adi Dottorato di Manuele Martini Relatore Interno: Prof. Aldo Altamore Relatore Esterno: Dr. Simone Dell’Agnello, LNF-INFN Coordinatore: Prof. Roberto Raimondi Anno Accademico 2015/2016 Alla mia famiglia... Contents List of Acronyms v Preface vii Why this work at LNF-INFN . vii Whatmycontributionis ............................ viii Workinthefieldofoptics ........................ ix Industrial & quality assurance . ix Physics analysis . x 1 Satellite/Lunar Laser Ranging 1 1.1 The ILRS . 2 1.2 Howitworks ............................... 4 1.3 Corner Cube Retroreflectors . 6 1.3.1 Apollo & Lunokhod Corner Cube Retroreflector (CCR) . 8 2GeneralRelativitytests 11 2.1 TestsoriginallyproposedbyEinstein . 11 2.1.1 Mercury perihelion precession . 11 2.1.2 Deflection of light . 12 2.1.3 Gravitational redshift . 18 i 2.1.4 Shapirotimedelay ........................ 20 2.2 ParametrizedPost-Newtonianformalism . 20 3 The SCF Lab 23 3.1 SCF-GCryostat.............................. 25 3.2 Vacuum & Cryogenic System . 27 3.3 Control and acquisition electronics . 30 3.4 Solar Simulator . 33 3.5 IR Thermacam . 36 3.6 Optical layout . 40 3.6.1 Angularcalibration . 42 4 The MoonLIGHT-2 experiment 45 4.1 MoonLIGHT-ILN............................. 46 4.2 MoonLIGHT-2payload. 49 4.2.1 Optical modeling . 49 4.3 Structural design . 55 4.3.1 Sunshade vs sunshade-less . 58 4.3.2 Falcon-9 test . 61 4.3.3 Actual Moon Laser Instrumentation for General relativity High accuracyTests(MoonLIGHT)-2design . 65 4.4 INRRI................................... 65 5 The SCF-TEST 69 5.1 The MoonLIGHT-2 SCF-TESTs: general description .
    [Show full text]
  • FTIR Reflection Techniques
    FT-IR Reflection Techniques Vladimír Setnička Overview – Main Principles of Reflection Techniques Internal Reflection External Reflection Summary Differences Between Transmission and Reflection FT-IR Techniques Transmission: • Excellent for solids, liquids and gases • The reference method for quantitative analysis • Sample preparation can be difficult Reflection: • Collect light reflected from an interface air/sample, solid/sample, liquid/sample • Analyze liquids, solids, gels or coatings • Minimal sample preparation • Convenient for qualitative analysis, frequently used for quantitative analysis FT-IR Reflection Techniques Internal Reflection Spectroscopy: Attenuated Total Reflection (ATR) External Reflection Spectroscopy: Specular Reflection (smooth surfaces) Combination of Internal and External Reflection: Diffuse Reflection (DRIFTs) (rough surfaces) FT-IR Reflection Techniques • Infrared beam reflects from a interface via total internal reflectance • Sample must be in optical contact with the crystal • Collected information is from the surface • Solids and powders, diluted in a IR transparent matrix if needed • Information provided is from the bulk matrix • Sample must be reflective or on a reflective surface • Information provided is from the thin layers Attenuated Total Reflection (ATR) - introduced in the 1960s, now widely used - light introduced into a suitable prism at an angle exceeding the critical angle for internal reflection an evanescent wave at the reflecting surface • sample in close contact Single Bounce ATR with IRE
    [Show full text]
  • Reflectance IR Spectroscopy, Khoshhesab
    11 Reflectance IR Spectroscopy Zahra Monsef Khoshhesab Payame Noor University Department of Chemistry Iran 1. Introduction Infrared spectroscopy is study of the interaction of radiation with molecular vibrations which can be used for a wide range of sample types either in bulk or in microscopic amounts over a wide range of temperatures and physical states. As was discussed in the previous chapters, an infrared spectrum is commonly obtained by passing infrared radiation through a sample and determining what fraction of the incident radiation is absorbed at a particular energy (the energy at which any peak in an absorption spectrum appears corresponds to the frequency of a vibration of a part of a sample molecule). Aside from the conventional IR spectroscopy of measuring light transmitted from the sample, the reflection IR spectroscopy was developed using combination of IR spectroscopy with reflection theories. In the reflection spectroscopy techniques, the absorption properties of a sample can be extracted from the reflected light. Reflectance techniques may be used for samples that are difficult to analyze by the conventional transmittance method. In all, reflectance techniques can be divided into two categories: internal reflection and external reflection. In internal reflection method, interaction of the electromagnetic radiation on the interface between the sample and a medium with a higher refraction index is studied, while external reflectance techniques arise from the radiation reflected from the sample surface. External reflection covers two different types of reflection: specular (regular) reflection and diffuse reflection. The former usually associated with reflection from smooth, polished surfaces like mirror, and the latter associated with the reflection from rough surfaces.
    [Show full text]
  • 581 01 Linkgping INSUHUILUTOL Swedish Road and Traffic Research Institut
    ISSN 0347-6030 V/]/rapport 323 A 1989 Visibility distances to retrore- flectors in opposing situations between two motor vehicles at night Gabriel Helmers and Sven - Olof Lundkvist an Vag-och Irafik- Statens vag- och trafikinstitut (VTI) * 581 01 LinkGping E INSUHUILUTOL swedish Road and Traffic Research Institute « $-581 01 Linkoping Sweden l/TIra A 1.989 Visibility distances to retrore- flectors in apposing situations between two motor vehicles at night Gabriel Helmers and Sven - Olaf Lundkvist f 00/! Statens veg- och trafikinstitut (VT/l - 581 01 Lin/(oping 'lSt/tlltet Swedish Road and Traffic Research Institute - 8-581 07 Linképing Sweden PREFACE This report is a shortened English version of the original final report in Swedish (VTI rapport 323). The research work as well as the work on the translation into English were sponsored by The Swedish Transport Research Board. Christina Ruthger had the main responsibility for the translation and editing of the report. VTI REPORT 323A CONTENTS Page ABSTRACT SUMMARY II BACKGROUND AND PROBLEM Safe visibility distance H Visibility in vehicle lighting Design traffic situation for the evaluation of IIIHIII thl retroreflectors and other visibility promoting measures ISSUES N METHOD Method for the measurement of visibility distances Experimental design Retroreflectors in the experiment Test design Headlights Low beam aiming Subjects NNNNNNNH Model of the analysis of variance wwwwwwwww 03014:.me RESULTS Large retroreflectors Small retroreflectors NNH bub-bub Analysis of variance concerning SMALL
    [Show full text]
  • Structure of Cone Photoreceptors
    Progress in Retinal and Eye Research 28 (2009) 289–302 Contents lists available at ScienceDirect Progress in Retinal and Eye Research journal homepage: www.elsevier.com/locate/prer Structure of cone photoreceptors Debarshi Mustafi a, Andreas H. Engel a,b, Krzysztof Palczewski a,* a Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106-4965, USA b Center for Cellular Imaging and Nanoanalytics, M.E. Mu¨ller Institute, Biozentrum, WRO-1058, Mattenstrasse 26, CH 4058 Basel, Switzerland abstract Keywords: Although outnumbered more than 20:1 by rod photoreceptors, cone cells in the human retina mediate Cone photoreceptors daylight vision and are critical for visual acuity and color discrimination. A variety of human diseases are Rod photoreceptors characterized by a progressive loss of cone photoreceptors but the low abundance of cones and the Retinoids absence of a macula in non-primate mammalian retinas have made it difficult to investigate cones Retinoid cycle directly. Conventional rodents (laboratory mice and rats) are nocturnal rod-dominated species with few Chromophore Opsins cones in the retina, and studying other animals with cone-rich retinas presents various logistic and Retina technical difficulties. Originating in the early 1900s, past research has begun to provide insights into cone Vision ultrastructure but has yet to afford an overall perspective of cone cell organization. This review Rhodopsin summarizes our past progress and focuses on the recent introduction of special mammalian models Cone pigments (transgenic mice and diurnal rats rich in cones) that together with new investigative techniques such as Enhanced S-cone syndrome atomic force microscopy and cryo-electron tomography promise to reveal a more unified concept of cone Retinitis pigmentosa photoreceptor organization and its role in retinal diseases.
    [Show full text]