DOCSLIB.ORG

Chromatic Aberrations in Optical Systems: Prediction and Correction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chromatic Aberrations in Optical Systems: Prediction and Correction Provided by the author(s) and NUI Galway in accordance with publisher policies. Please cite the published version when available. Title Chromatic Aberrations in Optical Systems: Prediction and Correction Author(s) Bahrami, Mehdi Publication Date 2012-12-19 Item record http://hdl.handle.net/10379/3463 Downloaded 2021-09-26T11:41:24Z Some rights reserved. For more information, please see the item record link above. Chromatic Aberrations in Optical Systems: Prediction and Correction by Mehdi Bahrami Supervisor: Dr. Alexander V. Goncharov A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy, School of Physics, Science Faculty, National University of Ireland, Galway December 2012 Abstract The variation of refractive index with wavelength, known as dispersion, was what redirected Isaac Newton from refractive telescope designs toward a reflective one, since he found the chromatic effect incurable. Later it was shown that different ma- terials demonstrate different chromatic characteristics and refractive optical elements can compensate each other’s chromatic contributions. This promoted the simple dis- persion effect to the field of formulizing and categorizing chromatic aberrations and their corrections. In this study an introduction to this process is provided, where the historical aspects are followed by the mathematical derivation and description of dif- ferent kinds of chromatic aberrations accompanied with a variety of approaches to correct the chromatic effects in different levels. The provided mathematical basis is employed in studying three distinctive topics. In the first one the flexibility of refrac- tive elements is used to provide a middle-sized catadioptric telescope design with all-spherical surfaces. Employing a new combination of chromatic lens correctors, the image quality can be improved so that it becomes comparable to an equivalent aspheric Ritchey-Chrétien telescope design. As the second topic the atmospheric dis- persion and its effect in extremely large telescopes are discussed, where a new atmo- spheric dispersion corrector design is proposed. In the third task the chromatic be- havior in an inhomogeneous medium is considered. A new gradient refractive index lens model for the crystalline lens of the eye is established and a different approach in characterizing its chromatic effects is developed. These three research topics are underpinning the main goal of the theses, that is the role of chromatic aberration in image formation in various optical systems. i List of publications Paper I: Mehdi Bahrami and Alexander V. Goncharov: All-spherical catadioptric telescope design for wide-field imaging Applied Optics, Vol. 49, Issue 30, pp. 5705-5712 (2010) Paper II: Mehdi Bahrami and Alexander V. Goncharov: The achromatic design of an atmospheric dispersion corrector for extremely large telescopes Optics Express, Vol. 19, Issue 18, pp. 17099-17113 (2011) Paper III: Mehdi Bahrami and Alexander V. Goncharov: Geometry-invariant gradient refractive index lens: analytical ray tracing Journal of Biomedical Optics, Vol. 17, Issue 5, pp. 55001-55009 (2012) Paper IV: Mehdi Bahrami and Alexander V. Goncharov: Geometry-invariant GRIN lens: iso-dispersive contours Biomedical Optics Express, Vol. 3, Issue 7, pp. 1684-1700 (2012) ii Acknowledgements This research was supported by Science Foundation Ireland under grant number 07/IN.1/1906. I express my sincerest gratitude to my supervisor, Dr. Alexander Goncharov, who has supported me throughout my research with his kindness, patience and knowledge whilst allowing me the freedom to work in my own way. I would like to thank Prof. Chris Dainty for providing a marvelous atmosphere and environment in the Applied Optics Group and for his valuable comments and ad- vices. The greatest appreciations to Dr. Hamid Fallah, who I am indebted to forever, who was the most help in the worst days. Thanks to my best friends Meisam, Javad, Hamed, Vahid, Maysam, Hossein, Reza, Vahid, and Marwan. Most of all, thanks to my parents, my brother, my sister, and my supportive wife for everything they have done for me. I will not forget all the love and the support that you have given me throughout my life and education. Thank you all. iii Acronyms ADC Atmospheric Dispersion Corrector AO Adaptive Optics ELT Extremely Large Telescope E-ELT The European Extremely Large Telescope GIGL Geometry-Invariant Gradient Refractive Index Lens GMT Giant Magellan Telescope GRIN Gradient Refractive Index LADC Linear Atmospheric Dispersion Corrector LGS Laser Guide Star OPD Optical Path Difference OPL Optical Path Length OT Optical Transmittance OT∗ Normalized Optical Transmittance RADC Rotating Atmospheric Dispersion Corrector RC Ritchey-Chrétien TMT Thirty Meter Telescope iv Contents Abstract i List of publications ii Acknowledgements iii Acronyms iv 1 Chromatic Aberrations 1 1.1 Historical aspects . .1 1.2 Axial color and achromats . .2 1.2.1 Axial chromatic aberration coefficients . .4 1.2.2 Achromats . .6 1.3 Secondary spectrum and apochromats . 11 1.3.1 Secondary spectrum . 11 1.3.2 Apochromats . 13 1.4 Lateral color . 15 1.5 Chromatic aberrations of a single surface . 18 1.6 Chromatic aberrations of a plane parallel plate . 20 1.7 Chromatic variations of Seidel aberrations . 21 v 2 Publications overview 23 2.1 Paper I . 23 2.2 Paper II . 25 2.3 Paper III . 28 2.4 Paper IV . 31 3 Conclusions, future work 33 Appendix 37 Bibliography 38 vi Chromatic Aberrations 1.1 Historical aspects The refractive index of any medium (other than vacuum) varies with wavelength. This means that all the optical properties of a medium are functions of wavelength. Traditionally, chromatic variations of paraxial properties such as image position and magnification have been considered as chromatic aberrations as well as variations of classical aberrations. These chromatic effects are usually the main problem in re- fractive systems. A well corrected refractive monochromatic imaging system could easily lose its acceptable optical performance even in a small range of wavelengths. Isaac Newton considered this problem intrinsically intractable and turned to reflec- tive systems. In fact, he thought that the chromatic aberrations of all lenses were proportional to their powers, with the same constant of proportionality even for dif- ferent glasses. Newton was the first to discuss chromatic aberrations in detail in his book, OPTICKS [1], which was released to the public in 1704. Newton’s conclusion was not the final word on this topic. Before Newton, it was a common belief that the human eye, because of containing different refractive me- dia, is optically corrected for chromatic aberration. James Gregory, the designer of the Gregorian telescope, had the same opinion in the 1660s. In addition to this, Christian Huygens had shown, in correspondence with Sir Christopher Wren in the 1660s, that a positive and a negative lens more or less in contact could correct spherical aberra- tion [2]. In 1729 Chester Moore Hall, a lawyer, followed on these two and could find a combination of positive and negative lenses made from different glasses, which pro- vided achromatic correction. He had such objectives made by opticians, and proved Newton wrong. In 1858 John Dollond, who expanded Hall’s work by experimenting with prisms, patented an achromatic lens [3]. From a technical point of view, manufacturing an acceptable reflective surface is much harder than a refractive element. The first practical reflective telescope was 1 1. Chromatic Aberrations built by Newton in 1668, 58 years after manufacturing the Galilean telescope (Al- though Zucchi made his reflective telescope in 1616, its image quality was not compa- rable to the refractive ones [4].) As manufactures approached 1 m objective doublets, in addition to being limited by mechanical difficulties of building large lenses, they faced another limitation related to difference in dispersion of the glasses used. In fact by, making larger and larger telescope doublet objectives they found that an achro- matic doublet was not quite free of chromatic aberration, and a residual error, known as secondary spectrum appeared. This led to the re-introduction of reflective objectives which are now universally used for apertures exceeding 1 m. From an optical designer’s point of view, the natural reaction to this new problem is adding one more lens to the doublet, thus making it an Apochromatic triplet. Imple- menting this solution was not simple because of the complexity of physics laws in dis- persion and the number of constraints which should be satisfied. On the other hand, the variety of glass combinations which can remove the residual chromatic aberra- tions is limited and sometimes expensive. Nevertheless this solution is implemented nowadays, and achromatic and apochromatic elements are used widely in optical sys- tems (e.g. small size telescope objectives, telescope correctors, photographic lenses, etc.). Before finishing this brief historical review, it is worth mentioning that a chromat- icly aberrated optical system or element is sometimes desired. For instance, when we need to compensate the chromatic aberration arising from the prior optical elements or media, for example the Earth’s atmosphere or human eye. 1.2 Axial color and achromats In the design and analysis of visual systems, it is common to choose F (blue, l = 486 nm), d (yellow, l = 588 nm), and C (red, l = 656 nm) spectral lines for the calculations. Fig. 1.1 shows that in a positive singlet, focus for F light is inside the paraxial focus for d light, while the C one lies on the outside. In fact, primary axial color is defined as the distance between the foci for F and C. To formulize this as a function of lens parameters one can start from a thin lens power equation [5], f = (n − 1)(C1 − C2), (1.1) 2 1. Chromatic Aberrations F d C Transverse axial color Primary Axial Color (Longitudinal axial color) Figure 1.1: F (blue), d (yellow), and C (red) spectral lines and their different foci. Primary axial color is the distance between the foci for F and C.
Load more

Recommended publications
  • The Walman Optical Perspective on High Index Lenses
    Optical Perspective of Polycarbonate Material JP Wei, Ph. D. November 2011 Introduction Among the materials developed for eyeglasses, polycarbonate is one that has a number of very unique properties and provides real benefits to eyeglass wearers. Polycarbonate lenses are not only cosmetically thinner, lighter, and provide superior impact-resistance, but also produce sharp optical clarity for both central and peripheral vision. It is well-known that as the index of refraction increases dispersion also increases. In other words, the higher the refractive index, the low the ABBE value. An increase in dispersion will cause an increase in chromatic aberration. Therefore, one of the concerns in the use of lens materials such as polycarbonate is: will chromatic aberration negatively affect patient adaption? MID 1.70 LENS MATERIAL CR39 TRIVEX INDEX POLYCARBONATE 1.67 INDEX INDEX REFRACTIVE INDEX 1.499 1.529 1.558 1.586 1.661 1.700 ABBE VALUES 58 45 37 30 32 36 The refractive index of a material is often abbreviated “n.” Except for air, which has a refractive index of approximately 1, the refractive index of most substances is greater than 1 (n > 1). Water, for instance, has a refractive index of 1.333. The higher the refractive index of a lens material, the slower the light will travel through it. While it is commonly recognized that high index materials will have greater chromatic aberration than CR-39 or low refractive index lenses, there has been no quantification of the amount of visual acuity loss that results from chromatic aberration. The purpose of this paper is to review the optical properties of polycarbonate material, its advantages over other lens materials, and the impact of chromatic aberration caused by the relative low ABBE value of the material on vision and clinical significance.
    [Show full text]
  • Chapter 3 (Aberrations)
    Chapter 3 Aberrations 3.1 Introduction In Chap. 2 we discussed the image-forming characteristics of optical systems, but we limited our consideration to an infinitesimal thread- like region about the optical axis called the paraxial region. In this chapter we will consider, in general terms, the behavior of lenses with finite apertures and fields of view. It has been pointed out that well- corrected optical systems behave nearly according to the rules of paraxial imagery given in Chap. 2. This is another way of stating that a lens without aberrations forms an image of the size and in the loca- tion given by the equations for the paraxial or first-order region. We shall measure the aberrations by the amount by which rays miss the paraxial image point. It can be seen that aberrations may be determined by calculating the location of the paraxial image of an object point and then tracing a large number of rays (by the exact trigonometrical ray-tracing equa- tions of Chap. 10) to determine the amounts by which the rays depart from the paraxial image point. Stated this baldly, the mathematical determination of the aberrations of a lens which covered any reason- able field at a real aperture would seem a formidable task, involving an almost infinite amount of labor. However, by classifying the various types of image faults and by understanding the behavior of each type, the work of determining the aberrations of a lens system can be sim- plified greatly, since only a few rays need be traced to evaluate each aberration; thus the problem assumes more manageable proportions.
    [Show full text]
  • Making Your Own Astronomical Camera by Susan Kern and Don Mccarthy
    www.astrosociety.org/uitc No. 50 - Spring 2000 © 2000, Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, CA 94112. Making Your Own Astronomical Camera by Susan Kern and Don McCarthy An Education in Optics Dissect & Modify the Camera Loading the Film Turning the Camera Skyward Tracking the Sky Astronomy Camp for All Ages For More Information People are fascinated by the night sky. By patiently watching, one can observe many astronomical and atmospheric phenomena, yet the permanent recording of such phenomena usually belongs to serious amateur astronomers using moderately expensive, 35-mm cameras and to scientists using modern telescopic equipment. At the University of Arizona's Astronomy Camps, we dissect, modify, and reload disposed "One- Time Use" cameras to allow students to study engineering principles and to photograph the night sky. Elementary school students from Silverwood School in Washington state work with their modified One-Time Use cameras during Astronomy Camp. Photo courtesy of the authors. Today's disposable cameras are a marvel of technology, wonderfully suited to a variety of educational activities. Discarded plastic cameras are free from camera stores. Students from junior high through graduate school can benefit from analyzing the cameras' optics, mechanisms, electronics, light sources, manufacturing techniques, and economics. Some of these educational features were recently described by Gene Byrd and Mark Graham in their article in the Physics Teacher, "Camera and Telescope Free-for-All!" (1999, vol. 37, p. 547). Here we elaborate on the cameras' optical properties and show how to modify and reload one for astrophotography. An Education in Optics The "One-Time Use" cameras contain at least six interesting optical components.
    [Show full text]
  • A N E W E R a I N O P T I
    A NEW ERA IN OPTICS EXPERIENCE AN UNPRECEDENTED LEVEL OF PERFORMANCE NIKKOR Z Lens Category Map New-dimensional S-Line Other lenses optical performance realized NIKKOR Z NIKKOR Z NIKKOR Z Lenses other than the with the Z mount 14-30mm f/4 S 24-70mm f/2.8 S 24-70mm f/4 S S-Line series will be announced at a later date. NIKKOR Z 58mm f/0.95 S Noct The title of the S-Line is reserved only for NIKKOR Z lenses that have cleared newly NIKKOR Z NIKKOR Z established standards in design principles and quality control that are even stricter 35mm f/1.8 S 50mm f/1.8 S than Nikon’s conventional standards. The “S” can be read as representing words such as “Superior”, “Special” and “Sophisticated.” Top of the S-Line model: the culmination Versatile lenses offering a new dimension Well-balanced, of the NIKKOR quest for groundbreaking in optical performance high-performance lenses Whichever model you choose, every S-Line lens achieves richly detailed image expression optical performance These lenses bring a higher level of These lenses strike an optimum delivering a sense of reality in both still shooting and movie creation. It offers a new This lens has the ability to depict subjects imaging power, achieving superior balance between advanced in ways that have never been seen reproduction with high resolution even at functionality, compactness dimension in optical performance, including overwhelming resolution, bringing fresh before, including by rendering them with the periphery of the image, and utilizing and cost effectiveness, while an extremely shallow depth of field.
    [Show full text]
  • High-Quality Computational Imaging Through Simple Lenses
    High-Quality Computational Imaging Through Simple Lenses Felix Heide1, Mushfiqur Rouf1, Matthias B. Hullin1, Bjorn¨ Labitzke2, Wolfgang Heidrich1, Andreas Kolb2 1University of British Columbia, 2University of Siegen Fig. 1. Our system reliably estimates point spread functions of a given optical system, enabling the capture of high-quality imagery through poorly performing lenses. From left to right: Camera with our lens system containing only a single glass element (the plano-convex lens lying next to the camera in the left image), unprocessed input image, deblurred result. Modern imaging optics are highly complex systems consisting of up to two pound lens made from two glass types of different dispersion, i.e., dozen individual optical elements. This complexity is required in order to their refractive indices depend on the wavelength of light differ- compensate for the geometric and chromatic aberrations of a single lens, ently. The result is a lens that is (in the first order) compensated including geometric distortion, field curvature, wavelength-dependent blur, for chromatic aberration, but still suffers from the other artifacts and color fringing. mentioned above. In this paper, we propose a set of computational photography tech- Despite their better geometric imaging properties, modern lens niques that remove these artifacts, and thus allow for post-capture cor- designs are not without disadvantages, including a significant im- rection of images captured through uncompensated, simple optics which pact on the cost and weight of camera objectives, as well as in- are lighter and significantly less expensive. Specifically, we estimate per- creased lens flare. channel, spatially-varying point spread functions, and perform non-blind In this paper, we propose an alternative approach to high-quality deconvolution with a novel cross-channel term that is designed to specifi- photography: instead of ever more complex optics, we propose cally eliminate color fringing.
    [Show full text]
  • Correlation of the Abbe Number, the Refractive Index, and Glass Transition Temperature to the Degree of Polymerization of Norbornane in Polycarbonate Polymers
    polymers Article Correlation of the Abbe Number, the Refractive Index, and Glass Transition Temperature to the Degree of Polymerization of Norbornane in Polycarbonate Polymers Noriyuki Kato 1,2,*, Shinya Ikeda 1, Manabu Hirakawa 1 and Hiroshi Ito 2,3 1 Mitsubishi Gas Chemical Company, 2-5-2 Marunouchi, Chiyoda-ku, Tokyo 100-8324, Japan; [email protected] (S.I.); [email protected] (M.H.) 2 Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan; [email protected] 3 Graduate School of Organic Materials Science, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan * Correspondence: [email protected] Received: 1 September 2020; Accepted: 16 October 2020; Published: 26 October 2020 Abstract: The influences of the average degree of polymerization (Dp), which is derived from Mn and terminal end group, on optical and thermal properties of various refractive indexed transparent polymers were investigated. In this study, we selected the alicyclic compound, Dinorbornane dimethanol (DNDM) homo polymer, because it has been used as a representative monomer in low refractive index polymers for its unique properties. DNDM monomer has a stable amorphous phase and reacts like a polymer. Its unique reaction allows continuous investigation from monomer to polymer. For hydroxy end group and phenolic end group polymers, the refractive index (nd) decreased with increasing Dp, and both converged to same value in the high Dp region. However, the Abbe number (νd) of a hydroxy end group polymer is not dependent on Dp, and the νd of a phenolic end group polymer is greatly dependent on Dp.
    [Show full text]
  • Tessar and Dagor Lenses
    Tessar and Dagor lenses Lens Design OPTI 517 Prof. Jose Sasian Important basic lens forms Petzval DB Gauss Cooke Triplet little stress Stressed with Stressed with Low high-order Prof. Jose Sasian high high-order aberrations aberrations Measuring lens sensitivity to surface tilts 1 u 1 2 u W131 AB y W222 B y 2 n 2 n 2 2 1 1 1 1 u 1 1 1 u as B y cs A y 1 m Bstop ystop n'u' n 1 m ystop n'u' n CS cs 2 AS as 2 j j Prof. Jose Sasian Lens sensitivity comparison Coma sensitivity 0.32 Astigmatism sensitivity 0.27 Coma sensitivity 2.87 Astigmatism sensitivity 0.92 Coma sensitivity 0.99 Astigmatism sensitivity 0.18 Prof. Jose Sasian Actual tough and easy to align designs Off-the-shelf relay at F/6 Coma sensitivity 0.54 Astigmatism sensitivity 0.78 Coma sensitivity 0.14 Astigmatism sensitivity 0.21 Improper opto-mechanics leads to tough alignment Prof. Jose Sasian Tessar lens • More degrees of freedom • Can be thought of as a re-optimization of the PROTAR • Sharper than Cooke triplet (low index) • Compactness • Tessar, greek, four • 1902, Paul Rudolph • New achromat reduces lens stress Prof. Jose Sasian Tessar • The front component has very little power and acts as a corrector of the rear component new achromat • The cemented interface of the new achromat: 1) reduces zonal spherical aberration, 2) reduces oblique spherical aberration, 3) reduces zonal astigmatism • It is a compact lens Prof. Jose Sasian Merte’s Patent of 1932 Faster Tessar lens F/5.6 Prof.
    [Show full text]
  • Applied Physics I Subject Code: PHY-106 Set: a Section: …………………………
    Test-1 Subject: Applied Physics I Subject Code: PHY-106 Set: A Section: ………………………….. Max. Marks: 30 Registration Number: ……………… Max. Time: 45min Roll Number: ………………………. Question 1. Define systematic and random errors. (5) Question 2. In an experiment in determining the density of a rectangular block, the dimensions of the block are measured with a vernier caliper with least count of 0.01 cm and its mass is measured with a beam balance of least count 0.1 g, l = 5.12 cm, b = 2.56 cm, t = 0.37 cm and m = 39.3 g. Report correctly the density of the block. (10) Question 3. Derive a relation to overcome chromatic aberration for an optical system consisting of two convex lenses. (5) Question 4. An achromatic doublet of focal length 20 cm is to be made by placing a convex lens of borosilicate crown glass in contact with a diverging lens of dense flint glass. Assuming nr = 1.51462, nb = ′ ′ 1.52264, 푛푟 = 1.61216, and 푛푏 = 1.62901, calculate the focal length of each lens; here the unprimed and the primed quantities refer to the borosilicate crown glass and dense flint glass, respectively. (10) Test-1 Subject: Applied Physics I Subject Code: PHY-106 Set: B Section: ………………………….. Max. Marks: 30 Registration Number: ……………… Max. Time: 45min Roll Number: ………………………. Question 1. Distinguish accuracy and precision with example. (5) Question 2. Obtain an expression for chromatic aberration in the image formed by paraxial rays. (5) Question 3. It is required to find the volume of a rectangular block. A vernier caliper is used to measure the length, width and height of the block.
    [Show full text]
  • Development of Highly Transparent Zirconia Ceramics
    11 Development of highly transparent zirconia ceramics Isao Yamashita ＊1 Masayuki Kudo ＊1 Koji Tsukuma ＊1 Highly transparent zirconia ceramics were developed and their optical and mechanical properties were comprehensively studied. A low optical haze value (H<1.0 %), defined as the diffuse transmission divided by the total forward transmission, was achieved by using high-purity powder and a novel sintering process. Theoretical in-line transmission (74 %) was observed from the ultraviolet–visible region up to the infra-red region; an absorption edge was found at 350 nm and 8 µm for the ultraviolet and infrared region, respectively. A colorless sintered body having a high refractive index (n d = 2.23) and a high Abbe’s number (νd = 27.8) was obtained. A remarkably large dielectric constant (ε = 32.7) with low dielectric loss (tanδ = 0.006) was found. Transparent zirconia ceramics are candidates for high-refractive index lenses, optoelectric devices and infrared windows. Transparent zirconia ceramics also possess excellent mechanical properties. Various colored transparent zirconia can be used as exterior components and for complex-shaped gemstones. fabricating transparent cubic zirconia ceramics.9,13-19 1．Introduction Transparent zirconia ceramics using titanium oxide as Transparent and translucent ceramics have been a sintering additive were firstly reported by Tsukuma.15 studied extensively ever since the seminal work on However, the sintered body had poor transparency translucent alumina polycrystal by Coble in the 1960s.1 and low mechanical strength. In this study, highly Subsequently, researchers have conducted many transparent zirconia ceramics of high strength were studies to develop transparent ceramics such as MgO,2 developed.
    [Show full text]
  • Carl Zeiss Oberkochen Large Format Lenses 1950-1972
    Large format lenses from Carl Zeiss Oberkochen 1950-1972 © 2013-2019 Arne Cröll – All Rights Reserved (this version is from October 4, 2019) Carl Zeiss Jena and Carl Zeiss Oberkochen Before and during WWII, the Carl Zeiss company in Jena was one of the largest optics manufacturers in Germany. They produced a variety of lenses suitable for large format (LF) photography, including the well- known Tessars and Protars in several series, but also process lenses and aerial lenses. The Zeiss-Ikon sister company in Dresden manufactured a range of large format cameras, such as the Zeiss “Ideal”, “Maximar”, Tropen-Adoro”, and “Juwel” (Jewel); the latter camera, in the 3¼” x 4¼” size, was used by Ansel Adams for some time. At the end of World War II, the German state of Thuringia, where Jena is located, was under the control of British and American troops. However, the Yalta Conference agreement placed it under Soviet control shortly thereafter. Just before the US command handed the administration of Thuringia over to the Soviet Army, American troops moved a considerable part of the leading management and research staff of Carl Zeiss Jena and the sister company Schott glass to Heidenheim near Stuttgart, 126 people in all [1]. They immediately started to look for a suitable place for a new factory and found it in the small town of Oberkochen, just 20km from Heidenheim. This led to the foundation of the company “Opton Optische Werke” in Oberkochen, West Germany, on Oct. 30, 1946, initially as a full subsidiary of the original factory in Jena.
    [Show full text]
  • Glossary of Lens Terms
    GLOSSARY OF LENS TERMS The following three pages briefly define the optical terms used most frequently in the preceding Lens Theory Section, and throughout this catalog. These definitions are limited to the context in which the terms are used in this catalog. Aberration: A defect in the image forming capability of a Convex: A solid curved surface similar to the outside lens or optical system. surface of a sphere. Achromatic: Free of aberrations relating to color or Crown Glass: A type of optical glass with relatively low Lenses wavelength. refractive index and dispersion. Airy Pattern: The diffraction pattern formed by a perfect Diffraction: Deviation of the direction of propagation of a lens with a circular aperture, imaging a point source. The radiation, determined by the wave nature of radiation, and diameter of the pattern to the first minimum = 2.44 λ f/D occurring when the radiation passes the edge of an Where: obstacle. λ = Wavelength Diffraction Limited Lens: A lens with negligible residual f = Lens focal length aberrations. D = Aperture diameter Dispersion: (1) The variation in the refractive index of a This central part of the pattern is sometimes called the Airy medium as a function of wavelength. (2) The property of an Filters Disc. optical system which causes the separation of the Annulus: The figure bounded by and containing the area monochromatic components of radiation. between two concentric circles. Distortion: An off-axis lens aberration that changes the Aperture: An opening in an optical system that limits the geometric shape of the image due to a variation of focal amount of light passing through the system.
    [Show full text]
  • Trivex & Polycarbonate Lenses
    Trivex Trivex was originally developed for the military, as visual armor. PPG Industries took the technology and adapted it for the optical industry. Trivex is a urethane-based pre-polymer. PPG named the material Trivex because of its three main performance properties. The three main properties are superior optics, ultra- lightweight, and extreme strength. Trivex has a high abbe value. Abbe value is a measure of the dispersion or color distortion of light through a lens into its color elements. Abbe number can also be referred to as v-value. The higher the abbe number, the less dispersion, the lower the number, the more dispersion. Trivex has an abbe number of 43-45. This is significantly higher than polycarbonate. Polycarbonate's abbe number is 30. Trivex has a very high level of light transmittance. The level is 91.4%. This is one of the highest levels of all lens materials. The high percentage is a factor that directly affects the brightness, clarity, and crispness of Trivex. Trivex has a specific gravity of 1.11. Specific gravity is the weight in grams of one cubic centimeter of the material. Specific gravity is also referred to as density. The higher the number, the more dense, or heavy, a lens material is. Trivex has the lowest specific gravity of any commonly used lens material. This makes Trivex the lightest lens material. Trivex is 16% lighter than CR-39, 25% lighter than 1.66, and 8% lighter than polycarbonate! Trivex has a refractive index of 1.53. This allows for a thinner lens than a CR-39 lens.
    [Show full text]