DOCSLIB.ORG

Apochromatic Lenses for Near-Infrared Astronomical Instruments

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Apochromatic lenses for near-infrared astronomical instruments Deqing Ren Abstract. A method based on the Herzberger approach has been in- Jeremy R. Allington-Smith vestigated for the selection of glasses for the apochromatic correction at University of Durham near-infrared (NIR) wavelength. The method avoids the algebraic com- Department of Physics plexity and simplifies the glass selection processes. Doublet and triplet Durham DH1 3LE glass combinations can be chosen directly from the plot of partial disper- United Kingdom sion versus V number. Good combinations of NIR doublets and triplets E-mail: [email protected] are given. Design examples show that the method is practical and effi- cient. © 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)02103-0] Subject terms: optical design; infrared; lenses; optical glass; camera. Paper 980318 received Aug. 24, 1998; accepted for publication Oct. 21, 1998. 1 Introduction 2 Partial Dispersion and V Number of Glasses In optical design, the first step is to choose optical glasses For NIR glasses, the Sellmeier and Herzberger dispersion to correct chromatic aberration. The control of chromatic formulas are used to calculate the index of refraction. The aberration through the selection of glasses is one of the glass catalogs of various manufacturers, available in digital most extensively studied subjects in the field of lens form, can be used to fit the index data and calculate the design.1–14 Different glass selection methods have been in- coefficients of the dispersion formulas. Then, the dispersion vestigated at visible wavelengths that can yield apochro- formulas can be used to calculate the optical index at any matic and superachromatic lens systems. The term apochro- wavelength. The more data one enters, the more accurate matic and superachromatic mean paraxial color correction will be the fit. The glass index data in this paper are from the infrared glass catalog published with the Zemax optical at three and four wavelengths, respectively. One approach design program.15 These data are provided by Schott16 or uses the Buchdahl glass dispersion equation to select compiled from published sources,17 and their accuracy has glasses for systems of thin lenses that yield apochromatic been confirmed by Albert Feldman’s measurements.18 and superachromatic color correction. Robb and Mercado1 2 For infrared glasses, the Herzberger dispersion formula and Buchdahl use this method to choose two kinds of ma- is often used to calculate the glass index14: terials for a doublet. Another approach uses Herzberger’s relative-partial-dispersion–Abbe-number equation, which can also yield apochromatic and superachromatic color cor- n5A1BL1CL21Dl21El41Fl6, ~1! rection. Herzberger and Salzberg14 used this method to se- lect glasses that can yield the same performance. where L51/(l220.028). Schott uses the Herzberger for- However, most of these studies were done at visible mula to calculate its glasses for NIR. The three-term Sell- wavelengths. Little attention has been given to the near- meier dispersion formula can also be used to calculate the 19 infrared ~NIR! wavelengths ~1to2.5mm!. The use of dou- index of infrared glass with adequate accuracy : blets is often limited by the small number of available glasses and the inability of a doublet to achromatize over K l2 K l2 K l2 the whole NIR wavelength range. We have not found any 2 1 2 3 n 215 2 1 2 1 2 . ~2! paper about the choice of glasses for triplets for NIR astro- l 2L1 l 2L2 l 2L3 nomical instruments. The Buchdahl glass dispersion equa- tion is mathematically too complex for the selection of As is done for visible optical wavelengths, for infrared glasses for doublets. From the point of view of optical en- wavelengths the V number and partial dispersion are de- gineering, it is important to find a simple and practical fined for a stated spectral region l1,l2,l3 as method to choose glasses for chromatic-aberration correc- tion. n221 This paper investigates a method that uses Herzberger’s V5 , ~3! approach to choose glasses to design doublets and triplets n12n3 for apochromatic correction in the NIR wavelength range. Doublet glasses or triplet glasses can be chosen directly n22n3 form the partial-dispersion–V-number plot, without alge- P5 , ~4! braic complexity. Finally, two design examples are given. n12n3 Opt. Eng. 38(3) 537–542 (March 1999) 0091-3286/99/$10.00 © 1999 Society of Photo-Optical Instrumentation Engineers 537 Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 06/28/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Ren and Allington-Smith: Apochromatic lenses... Table 1 Refractive indices, V number, and partial dispersion of NIR glasses at 20°C. The refractive indices of IRG2, IRG3, IRG7, IRG9, and ZnSe were calculated with the Herzberger formula; the others, with the Sellmeier formula. The silica is fused silica; the ZnSe and ZnS are chemical vapor deposited. n1 n2 n3 V Glass (1.25 mm) (1.65 mm) (2.2 mm) number P silica 1.44748 1.44280 1.43501 35.5110 0.6246 LiF 1.38512 1.38190 1.37659 44.7701 0.6217 MgF2-O 1.37214 1.36995 1.36648 65.3879 0.6128 IRG9 1.47745 1.47461 1.47031 66.4437 0.6028 IRG7 1.54755 1.54279 1.53584 46.3737 0.5929 CaF2 1.42746 1.42556 1.42280 91.4696 0.5907 MgO 1.71941 1.71449 1.70762 60.6185 0.5824 IRG11 1.66140 1.65675 1.65060 60.8103 0.5699 Fig. 1 Plot of partial dispersion P versus V number for NIR glasses IRG3 1.81383 1.80709 1.79841 52.3309 0.5627 at wavelengths 1.25, 1.65, and 2.2 mmat20°C. BaF2 1.46719 1.46571 1.46396 144.4753 0.5412 IRG2 1.85741 1.85088 1.84321 59.9108 0.5400 SrTiO3 2.29795 2.28014 2.26082 34.4813 0.5203 ZnS 2.27935 2.26973 2.26338 79.4784 0.3974 NIR astronomical instruments work in the J, H, and K ZnSe 2.46802 2.45278 2.44368 59.7034 0.3739 bands ~which are also standard atmospheric windows of transparency21!. In order to avoid refocusing in the three bands, we choose the infrared wavelengths as l151.25 mm, l251.65 mm, l352.2 mm. where n1 , n2 , and n3 are the indices of refraction at the short wavelength l1 , central wavelength l2 , and long wavelength l3 , respectively. It is important to note that Using Eqs. ~1!, ~2!, ~3!, and ~4!, we can calculate the indi- l1 , l2 , and l3 are also the wavelengths to be corrected for ces, V number, and partial dispersion P of the most-used chromatic aberration. glasses in the NIR wavelength. The results are given in The plot of partial dispersion versus V number is ex- Table 1. All of these indices are for room temperature tremely important in choosing glasses that will permit sec- ~20°C!, and all of these glasses have high transmission. ondary color correction in a lens. Unfortunately, many A plot of V number versus partial dispersion at 20°C is glass catalogs provided with computer design programs shown in Fig. 1. It can be seen that BaF2, ZnS, and ZnSe ~such as Zemax! or by glass companies only provide glasses are far away from other glasses on the plot. This is V-number and P data that are calculated at the F-d-C wave- important in the choice of glass, as will be shown in Secs. lengths. In fact, these data are useless for glass selection, as 3 and 4. As NIR instruments are often operated at cryo- they will be different at visible and NIR wavelengths. genic temperatures, we also calculated the partial disper- Shannon20 has calculated V-number and P values of some sion and V number of all these glasses at 77 K and found visible optical glasses in different wavelength ranges. He that their relative values are almost unchanged. So the plot also compared the plots of V number versus P for these of V number versus partial dispersion at 20°C can be used glasses in the visible F-d-C and the infrared wavelength as a standard map for glass choice at other temperatures. ranges, and found that the glass distributions change dra- matically when the wavelength shifts to the infrared. Herzberger and Salzberg14 calculated the partial disper- 3 Selection of Glass for a Two-Material Doublet sion P of some infrared glasses in the wavelength range 1.5 For simplicity in application, only axial chromatic aberra- to 5.0 mm. He used 3.5 mm as the central wavelength l2 . tion will be considered. For thin lens doublets in close con- We find that the distributions of glasses on the V-versus-P tact or with a small air space, the conditions for three- 14 plot for differing short wavelength l1 , central wavelength wavelength color correction are l2 , and long wavelength l3 are also dramatically different, and this has generally been ignored. For example if l1 , l2 , F1 F2 and l3 are 1, 1.75, and 2.5 mm, respectively, the V-number 1 50, ~5! and P of CaF2 glass are 54.6 and 0.488, respectively, com- V1 V2 pared with 91.5 and 0.591 when l1 , l2 , and l3 are 1.25, 1.65, and 2.2 mm, respectively. So the V-number and P F F data must be calculated according to the wavelengths at 1 2 P11 P250, ~6! which one corrects for chromatic aberration. V1 V2 538 Optical Engineering, Vol. 38 No. 3, March 1999 Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 06/28/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Ren and Allington-Smith: Apochromatic lenses..
Recommended publications
  • The Walman Optical Perspective on High Index Lenses

    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.
  • Chapter 3 (Aberrations)

    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.
  • Simple Method for Measuring the Zero-Dispersion Wavelength in Optical Fibers Maxime Droques, Benoit Barviau, Alexandre Kudlinski, Géraud Bouwmans and Arnaud Mussot

    Simple Method for Measuring the Zero-Dispersion Wavelength in Optical Fibers Maxime Droques, Benoit Barviau, Alexandre Kudlinski, Géraud Bouwmans and Arnaud Mussot

    Simple Method for Measuring the Zero-Dispersion Wavelength in Optical Fibers Maxime Droques, Benoit Barviau, Alexandre Kudlinski, Géraud Bouwmans and Arnaud Mussot Abstract— We propose a very simple method for measuring the zero-dispersion wavelength of an optical fiber as well as the ratio between the third- and fourth-order dispersion terms. The method is based on the four wave mixing process when pumping the fiber in the normal dispersion region, and only requires the measurement of two spectra, provided that a source tunable near the zero- dispersion wavelength is available. We provide an experimental demonstration of the method in a photonic crystal fiber and we show that the measured zero-dispersion wavelength is in good agreement with a low-coherence interferometry measurement. Index Terms— Photonic crystal fiber, four-wave-mixing, chromatic dispersion, zero-dispersion wavelength. I. INTRODUCTION Group velocity dispersion (GVD) is one of the key characteristics of optical fibers. It is thus important to be able to accurately measure this parameter. The techniques developed to reach this goal can be divided into two main categories: the ones based on linear processes, such as time-of-flight, phase-shift or interferometric measurements [1-4]; and the ones based on nonlinear effects, such as four wave mixing (FWM), mainly [5-8]. The main advantage of these last ones is that the GVD measurement can be made in fiber samples ranging from a few meters up to hundred of meters long, while linear techniques are restricted to either very short samples (in the meter range) or to very long ones (in the kilometer range).
  • Tauc-Lorentz Dispersion Formula

    Tauc-Lorentz Dispersion Formula

    TN11 Tauc-Lorentz Dispersion Formula Spectroscopic ellipsometry (SE) is a technique based on the measurement of the relative phase change of re- flected and polarized light in order to characterize thin film optical functions and other properties. The meas- ured SE data are used to describe a model where layers refer to given materials. The model uses mathematical relations called dispersion formulae that help to evaluate the material’s optical properties by adjusting specific fit parameters. This technical note deals with Tauc-Lorentz dispersion formula. Theoretical model The real part εr,TL of the dielectric function is derived from the expression of εi using the Kramers-Kronig integration. Jellison and Modine developed this model (1996) using Then, it comes the following expression for εi: the Tauc joint density of states and the Lorentz oscillator. The complex dielectric function is : 2 ∞ ξ ⋅ε ()ξ ε ()E = ε ()∞ + ⋅ P ⋅ i dξ ()5 ~ε =ε + i ⋅ε =ε + i ⋅(ε × ε ) (1) r r π ∫ ξ 2 − E 2 TL r,TL i,TL r,TL i,T i, L Eg Here the imaginary part εi,TL of the dielectric function is where P is the Cauchy principal value containing the resi- given by the product of imaginary part of Tauc’s (1966) dues of the integral at poles located on lower half of the dielectric εi,T function with Lorentz one εi,L. In the approx- complex plane and along the real axis. imation of parabolic bands, Tauc’s dielectric function de- According to Jellison and Modine (Ref. 1), the derivation scribes inter-band transitions above the band edge as : of the previous integral yields : E − E 2 ⎛ g ⎞ 2 2 εi,T ()E > Eg = AT ⋅⎜ ⎟ ()2 A⋅C ⋅a ⎡ E + E + α ⋅ E ⎤ ⎜ E ⎟ ln 0 g g ⎝ ⎠ εr,TL ()E = ε∞ + 4 ⋅ln⎢ 2 2 ⎥ where : 2⋅π ⋅ζ ⋅α ⋅ E0 ⎣⎢ E0 + Eg − α ⋅ Eg ⎦⎥ -A is the Tauc coefficient T A a ⎡ ⎛ 2⋅ E + α ⎞ - E is the photon energy − ⋅ a tan ⋅ π − arctan⎜ g ⎟ + 4 ⎢ ⎜ ⎟ K -Eg is the optical band gap π ζ ⋅ E0 ⎣ ⎝ C ⎠ The imaginary part of Tauc’s dielectric function gives the ⎛ α − 2⋅ E ⎞⎤ response of the material caused by inter-band mecha- g + arctan⎜ ⎟⎥ nisms only : thus εi, T (E ≤ Eg) = 0.
  • Correlation of the Abbe Number, the Refractive Index, and Glass Transition Temperature to the Degree of Polymerization of Norbornane in Polycarbonate Polymers

    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.
  • Tessar and Dagor Lenses

    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.
  • Section 5: Optical Amplifiers

    Section 5: Optical Amplifiers

    SECTION 5: OPTICAL AMPLIFIERS 1 OPTICAL AMPLIFIERS S In order to transmit signals over long distances (>100 km) it is necessary to compensate for attenuation losses within the fiber. S Initially this was accomplished with an optoelectronic module consisting of an optical receiver, a regeneration and equalization system, and an optical transmitter to send the data. S Although functional this arrangement is limited by the optical to electrical and electrical to optical conversions. Fiber Fiber OE OE Rx Tx Electronic Amp Optical Equalization Signal Optical Regeneration Out Signal In S Several types of optical amplifiers have since been demonstrated to replace the OE – electronic regeneration systems. S These systems eliminate the need for E-O and O-E conversions. S This is one of the main reasons for the success of today’s optical communications systems. 2 OPTICAL AMPLIFIERS The general form of an optical amplifier: PUMP Power Amplified Weak Fiber Signal Signal Fiber Optical AMP Medium Optical Signal Optical Out Signal In Some types of OAs that have been demonstrated include: S Semiconductor optical amplifiers (SOAs) S Fiber Raman and Brillouin amplifiers S Rare earth doped fiber amplifiers (erbium – EDFA 1500 nm, praseodymium – PDFA 1300 nm) The most practical optical amplifiers to date include the SOA and EDFA types. New pumping methods and materials are also improving the performance of Raman amplifiers. 3 Characteristics of SOA types: S Polarization dependent – require polarization maintaining fiber S Relatively high gain ~20 dB S Output saturation power 5-10 dBm S Large BW S Can operate at 800, 1300, and 1500 nm wavelength regions.
  • Applied Physics I Subject Code: PHY-106 Set: a Section: …………………………

    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.
  • Examples of Translucent Objects

    Examples of Translucent Objects

    Examples Of Translucent Objects Chancier and ecclesiological Chan never nebulise his heroes! Afternoon and affirmable Garvin often arterialised some yokes glisteringly or nuggets jealously. Rationalist and papist Erastus attunes while frogged Robb descant her mercs anaerobically and misclassifies moistly. You wish them, a whole and water droplets in translucent materials, like to be directed to translucent, and translucency is pumpkin seed oil. Learn more energy when the error you found that is diffused and table into light? Light can see more light through the image used in illumination affects the number of the materials differ. Explain the examples of a technically precise result. Assigned two example, the teaching for online counselling session has. If the object scatters light. Opaque objects examples intersecting volumes clad in translucency rating increases with textiles and we examined the example of these materials, it can you? Learn from objects examples of translucency controls are called translucent object has a great instructors. Opaque materials which the example of light to authenticated users to work the question together your new class can exit this activity to contact with. Please reload this means cannot see through a lahu man smoking against the of examples of how the choice between a few moving parts that a meaning they transmit. You study the object is. Here ߤ and examples of object looktranslucent or water spray, they interact with every day. Raft product for example of objects, the patterns and to. Students to object, but it allows us improve the example of material appears here is. Emailing our online counselling session expired game yet when describing phenomena such objects? You some examples of translucency image as an example of.
  • Development of Highly Transparent Zirconia Ceramics

    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.
  • Carl Zeiss Oberkochen Large Format Lenses 1950-1972

    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.
  • Chapter 19/ Optical Properties

    Chapter 19/ Optical Properties

    Chapter 19 /Optical Properties The four notched and transpar- ent rods shown in this photograph demonstrate the phenomenon of photoelasticity. When elastically deformed, the optical properties (e.g., index of refraction) of a photoelastic specimen become anisotropic. Using a special optical system and polarized light, the stress distribution within the speci- men may be deduced from inter- ference fringes that are produced. These fringes within the four photoelastic specimens shown in the photograph indicate how the stress concentration and distribu- tion change with notch geometry for an axial tensile stress. (Photo- graph courtesy of Measurements Group, Inc., Raleigh, North Carolina.) Why Study the Optical Properties of Materials? When materials are exposed to electromagnetic radia- materials, we note that the performance of optical tion, it is sometimes important to be able to predict fibers is increased by introducing a gradual variation and alter their responses. This is possible when we are of the index of refraction (i.e., a graded index) at the familiar with their optical properties, and understand outer surface of the fiber. This is accomplished by the mechanisms responsible for their optical behaviors. the addition of specific impurities in controlled For example, in Section 19.14 on optical fiber concentrations. 766 Learning Objectives After careful study of this chapter you should be able to do the following: 1. Compute the energy of a photon given its fre- 5. Describe the mechanism of photon absorption quency and the value of Planck’s constant. for (a) high-purity insulators and semiconduc- 2. Briefly describe electronic polarization that re- tors, and (b) insulators and semiconductors that sults from electromagnetic radiation-atomic in- contain electrically active defects.