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Fundamental Optics Material Properties Optical Specifications Gaussian Beam Optics Optical Coatings Mechanical and Chemical Properties Mechanical and chemical properties of glass are important to lens manufacturers. These properties can also be significant to the user, especially when the component will be used in a harsh environment. Different polishing techniques and special handling may be needed depending on whether the glass is hard or soft, or whether it is extremely sensitive to acid or alkali. To quantify the chemical properties of glasses, each glass is rated according to four categories: climatic resistance, stain resistance, acid resistance, and alkali and phosphate resistance. Climatic Resistance Humidity can cause a cloudy film to appear on the surface of some optical glass. Climatic resistance expresses the susceptibility of a glass to this process. In this test, glass is placed in a watervapor-saturated environment and subjected to a temperature cycle which alternately causes condensation and evaporation. The glass is given a rating from 1 to 4 depending on the amount of surface scattering induced by the test. A rating of 1 indicates little or no change after seven days of exposure; a rating of 4 means a significant change occurred in less than 30 hours. Stain Resistance Stain resistance expresses resistance to mildly acidic water solutions, such as fingerprints or perspiration. In this test, a few drops of a mild acid are placed on the glass. A colored stain, caused by interference, will appear if the glass starts to decompose. A rating from 1 to 5 is given to each glass, depending on how much time elapses before stains occur. A rating of 1 indicates no observed stain in 100 hours of exposure; a rating of 5 means that staining occurred in less than 0.2 hours. Acid Resistance Acid resistance quantifies the resistance of a glass to stronger acidic solutions. Acid resistance can be particularly important to lens manufacturers because acidic solutions are typically used to strip coatings from glass or to separate cemented elements. A rating from 1 to 4 indicates progressively less resistance to a pH 0.3 acid solution, and values from 51 to 53 are used for glass with too little resistance to be tested with such a strong solution. Alkali and Phosphate Resistance Alkali resistance is also important to the lens manufacturer since the polishing process usually takes place in an alkaline solution. Phosphate resistance is becoming more significant as users move away from cleaning methods that involve chlorofluorocarbons (CFCs) to those that may be based on traditional phosphate-containing detergents. In each case, a two-digit number is used to designate alkali or phosphate resistance. The first number, from 1 to 4, indicates the length of time that elapses before any surface change occurs in the glass, and the second digit reveals the extent of the change. Microhardness The most important mechanical property of glass is microhardness. A precisely specified diamond scribe is placed on the glass surface under a known force. The indentation is then measured. The Knoop and the Vickers microhardness tests are used to measure the hardness of a polished surface and a freshly fractured surface, respectively. APPLICATION NOTE Glass Manufacturers The catalogs of optical glass manufacturers contain products covering a very wide range of optical characteristics. However, it should be kept in mind that the glass types that exhibit the most desirable properties in terms of index of refraction and dispersion often have the least practical chemical and mechanical characteristics. Furthermore, poor chemical and mechanical attributes translate directly into increased component costs because working these sensitive materials increases fabrication time and lowers yield. Please contact us before specifying an exotic glass in an optical design so that we can advise you of the impact that that choice will have on part fabrication. 4.6 1 Visit Us OnLine! www.mellesgriot.com
Melles Griot Lens Materials Melles Griot simple lenses are made of synthetic fused silica, BK7 grade A fine annealed glass, and several other materials. The following table identifies the materials used in Melles Griot lenses. Some of these materials are also used in prisms, mirror substrates, and other products. Glass type designations and physical constants are the same as those published by Schott Glass. Melles Griot occasionally uses corresponding glasses made by other glass manufacturers but only when this does not result in a significant change in optical properties. The quality of performance of optical lenses and prisms depends on the quality of the material used. No amount of skill during manufacture can eradicate striae, bubbles, inclusions, or variations in index. Melles Griot takes considerable care in its material selection, using only first-class optical materials from reputable glass manufacturers. The result is reliable, repeatable, consistent performance. The following physical constant values are reasonable averages based on historical experience. Individual material specimens may deviate from these means. Materials having tolerances more restrictive than those published in the rest of this chapter, or materials traceable to specific manufacturers, are available only on special request. BK7 OPTICAL GLASS A borosilicate crown glass, BK7, is the material used in many Melles Griot products. BK7 performs well in chemical tests so that special treatment during polishing is not necessary. BK7, relatively hard glass, does not scratch easily and can be handled without special precautions. The bubble and inclusion content of BK7 is very low: the bubble and inclusion content cross-section totals less than 0.029 mm 2 per 100 cm 3 . Another important characteristic of BK7 is its excellent transmittance, as low as 350 nm. Because of these properties, BK7 is used widely throughout the optics industry. A variant of BK7, designated UBK7, has transmission almost as low as 300 nm. This special glass is useful in applications requiring a high index of refraction, the desirable chemical properties of BK7, and transmission deeper into the ultraviolet range. Melles Griot Lens Materials Materials Synthetic Fused Silica, UV Grade Synthetic Fused Silica, Optical Quality BK7, Grade A Fine Annealed LaSF N9, Grade A Fine Annealed BaK1, Grade A Fine Annealed Optical Crown Low-Expansion Borosilicate Glass (LEBG) SF11, Grade A Fine Annealed SK11 and SF5, Grade A Fine Annealed Sapphire Zinc Selenide Various Glass Combinations Melles Griot reserves the right to make material changes or substitutions on any optical components without prior notice. Lens Product Numbers 01 LQC 01 LQP 01 LQD 01 LQS 01 LQB 01 LQT 01 LQF Selected 01 CMP series 01 LCN 01 LMN 01 LCP 01 LMP 01 LDK 01 LPK 01 LDX 01 LPX 01 LFS 01 LPX 401 01 LPX 411 01 LPX 405 01 LPX 413 01 LPX 407 06 LMS 01 LPX 415 01 LPX 423 01 LPX 421 01 LAG Selected 01 CMP series 06 LXP 06 LAI 01 LSX 12 LNZ 12 LPZ 01 LAL 04 EWR 001 01 LAO 04 OAS 01 LAT 04 OAP 01 LBX 06 DDL 04 ECW 06 DBF 04 EHY 06 GLC 04 EPP 06 GLR 04 ERA 001 09 LBM 04 EWA 09 LCM 04 EWP 001 09 LSL Fundamental Optics Gaussian Beam Optics Optical Specifications Material Properties Optical Coatings Visit Us Online! www.mellesgriot.com 1 4.7
Page 1 and 2:
Fundamental Optics 1 Introduction 1
Page 3 and 4:
Paraxial Formulas SIGN CONVENTIONS
Page 5 and 6:
object F 2 Figure 1.4 image Example
Page 7 and 8:
Figure 1.6 Figure 1.7 f f 2 object
Page 9 and 10:
Figure 1.8 Figure 1.9 INDIVIDUAL EL
Page 11 and 12: Performance Factors After paraxial
Page 13 and 14: third-order, monochromatic, spheric
Page 15 and 16: Positive lens elements usually have
Page 17 and 18: Lens Shape Aberrations described in
Page 19 and 20: ay f-numbers 2.7 3.3 4.4 6.7 13.3 S
Page 21 and 22: AIRY DISC DIAMETER = 2.44 l f/# Fig
Page 23 and 24: Lens Selection Having discussed the
Page 25 and 26: Example 4: Diffraction-Limited Perf
Page 27 and 28: Aberration Balancing To improve sys
Page 29 and 30: Definition of Terms FOCAL LENGTH (f
Page 31 and 32: infinity (which is a comfortable vi
Page 33 and 34: For symmetric lenses (r 2 = 4r 1 ),
Page 35 and 36: Separation of Nodal Point from Corr
Page 37 and 38: Gaussian Beam Optics 2 Introduction
Page 39 and 40: Even if a Gaussian TEM 00 laser-bea
Page 41 and 42: eam expander INCORPORATING M 2 INTO
Page 43 and 44: M 2 AND THE LENS EQUATION For real-
Page 45 and 46: employed when laser power must be c
Page 47 and 48: Figure 2.13 Keplerian beam expander
Page 49 and 50: Optical Specifications 3 Wavefront
Page 51 and 52: Centration The mechanical axis and
Page 53 and 54: PERFECT RECTANGULAR LENS The MDMTF
Page 55 and 56: The permissible number of maximum-s
Page 57 and 58: Material Properties 4 Material Prop
Page 59 and 60: Introduction Glass manufacturers pr
Page 61: maximum value for homogeneity withi
Page 65 and 66: Refractive Index of Five Schott Gla
Page 67 and 68: Synthetic Fused Silica Fused silica
Page 69 and 70: PERCENT INTERNAL TRANSMITTANCE 99.9
Page 71 and 72: Low-Expansion Borosilicate Glass Th
Page 73 and 74: ZERODUR ® Many optical application
Page 75 and 76: Optical Coatings 5 Optical Coatings
Page 77 and 78: OEM and Special Coatings Melles Gri
Page 79 and 80: PERCENT REFLECTANCE 100 90 80 70 60
Page 81 and 82: will depend on the ratio of optical
Page 83 and 84: v = angle of incidence PERCENT REFL
Page 85 and 86: PERCENT REFLECTANCE PER SURFACE 2.0
Page 87 and 88: Two-Layer Coatings of Arbitrary Thi
Page 89 and 90: ION-ASSISTED BOMBARDMENT Ion-assist
Page 91 and 92: Single-Layer MgF 2 Antireflection C
Page 93 and 94: PERCENT REFLECTANCE 5 4 3 2 1 norma
Page 95 and 96: EXTENDED-RANGE HEBBAR ANTIREFLECTIO
Page 97 and 98: V-Coatings V-coatings are multilaye
Page 99 and 100: Metallic High-Reflection Coatings W
Page 101 and 102: INTERNAL SILVER (/036) $ For intern
Page 103 and 104: Dielectric High-Reflection Coatings
Page 105 and 106: PERCENT REFLECTANCE 100 80 60 40 20
Page 107 and 108: MAXBRIte Coatings MAXBRIte (multi
Page 109 and 110: Laser-Line MAX-R Coatings These mu
Page 111 and 112: Ultrafast Coating Melles Griot has
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Optical Coatings

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