Optics and Optical Instruments—Preparation of drawings for optical elements and systems: A User's Guide 1557522715, 9781557522719

Citation preview

Optics and Optical Instruments—Preparation of drawings for optical elements and systems: A User's Guide OSA Standards Committee eds. Ronald K. Kimmel and Robert E. Parks

We hope you appreciate this republication of ISO 10110 Optics and Optical Instruments— Preparation of Drawings for Optical Elements and Systems: A User's Guide, first published in 1995. This open-access republication is intended to give you a feel for the ISO 10110 standard and an overview of its general scope and methodology. It is not intended for use as a standard as it is hopelessly out of date. Copyright 1995 When you have convinced yourself of the usefulness of ISO 10110, go to www.ISO.org or www.ANSI.org and order the standard. Yes, we know it is pricey, but it is a cost of doing business in the optics industry. Ultimately, using the standard will save you money. The advantage of using ISO 10110 is that the optics world is global and, if your drawings are done according to this standard, they will be more likely to be understood worldwide. If you find there are parts of ISO 10110 that put you to a disadvantage, or you have something to add to the standard, please contact Patrick Augino at the Optics and Electro-Optics Standards Council (OEOSC) [email protected] and join OEOSC. OEOSC is the US ANSI member of the ISO optical standards writing committee, TC172. As a member of OEOSC you will have the opportunity to work on updates to the standard and will receive proposed updates for review and approval. Respectfully, Robert E. Parks 4 May 2021

ISO 10110 Optics and Optical InstrumentsPreparation of drawings for optical elements and systems:

A User's Guide

Acknowledgments

The Standards Committee of the Optical Society of America would like to acknowledge the contributions of the authors of the User's Guide: Eugene Church, Jane Clover, Manfred Grinde!, Rudolf Hartmann, Gordon Kane, Ronald Kimmel, Robert Parks, SteveSeitel, Lars Selberg, Douglas Sinclair, Peter Takacs, and Patrick Trotta. Members of the Standards Committee during the 1984-1994 period provided many suggestions for improving the actual standard and a critical review of the User's Guide. Without their help, publication of this User's Guide would not be possible. Alan Tourtlotte and Kelly Furr of the OSA staff are to be thanked for their patience and persistence during the several years of creation of the User's Guide.

How to order ISO 10110

For copies of the published standard, contact American National Standards Institute 11 West 42nd Street, New York, New York 10036 Phone 212/642-4900 Fax 212/302-1286 Inquire to ANSI (Attention: Customer Service) for pricing and availability.

For copies of the draft standard, contact National Association of Photographic Manufacturers, Inc. 550 Mamaroneck Avenue, Harrison, New York 10528-1612 Phone 914/698-7603 Fax 914/698-7609 $10 per part Payment by check only

ISO 10110 Optics and Optical InstrumentsPreparation of drawings for optical elements and systems:

A User's Guide

By the OSA Standards Committee

Edited by Ronald K. Kimmel and Robert E. Parks

OSA.

Optical Society of America 2010 Massachusetts Avenue NW Washington DC 2003~1023

Portions of this publication may be cited in other publications. To facilitate access to the original publication source, the following form for reference citations is suggested: OSA Standards Committee, ISO 10110 Optics and Optical InstrumentsPreparation of drawings for optical elements and systems: A User's Guide, Ronald K. Kimmel and Robert E. Parks, eds. (Optical Society of America, Washington DC 1995), pp.xx-xx.

ISBN 1-55752-271-5 LC Number

93-85841

Copyright© 1995, Optical Society of America Individual readers of this work and libraries acting for them are permitted to make fair use of the material in it as specified by the 1978 U.S. Copyright Law. Permission is granted to quote from this book in scientific works with the customary acknowledgment of the source. Reproduction of figures and tables is likewise permitted in other articles and books provided that the same information is printed with them and notification is given to the Optical Society of America. The views and conclusions contained in this publication are those of the author and should not be interpreted as necessarily representing endorsements, either expressed or implied, of the Optical Society of America. Printed in the U.S.A. Third printing, July 1998

Table of Contents

lnhodudHon

1

Chapter 1

General Chapter 2

Material imperfedHons-Stress Birefringence

4 14

Chapter3

Material imperfedHons-Bubbles and inclusions

17

Chapter 4

Material imperfections-Inhomogeneity and striae

20

ChapterS

Surface form tolerances

23

Chapter6

Centring tolerances

35

Chapter 7

Surface imperfection tolerances

45

Chapter 8

Surface texture

50

Chapter9

Surface treatment and coating

63

Chapter 10

Tabular form

67

Chapter 11

Non-toleranced data

71

Chapter 12

Aspheric surfaces

75

Chapter 13

Laser irradiation damage threshold

80

Glossaty for ISO 10110 User's Guide

84

Introduction

The reader might legitimately ask, "If there is a standard, why should I read a handbook about it?" This Introduction is an attempt to answer that question. The new standard, ISO 10110 Optics and Optical Instruments- Preparation of drawings for optical elements and systems, contains only the bare essentials, but none of the background or reasoning that went into the formulation of the standard. Without some insight into the background of the standard, it may be difficult, or even impossible, to use effectively. Analogously, this handbook may be compared to the many self-help books that are published these days to explain what is meant in software manuals. Using only the manual, you may be able to play with the software, but you will not be able to use it effectively without additional background and guidance. In this vein, we will begin by giving some of the historical background as to why ISO 10110 was written. This background will also help explain the rather elaborate or cluttered looking drawings that result from using this standard. Even before that, we should explain where ISO itself came from and why there is a Technical Committee 172 for Optics and optical instruments. The first international standards organization was started in the late 1800's as the result of worldwide electrification. It was obvious that electrical grids and appliances would cross national boundaries, and that it made sense to tackle some of the potential problems that would limit or slow the growth of electrification before anyone had invested too much in hardware that might be made obsolete. This first truly international standards organization, the International Electro-technical Committee (IEC), was started with a scope that limited it to issues related to electricity, and later, electronics. For a long time, the IEC was the only voluntary international standards organization, but the organizational idealism that created the United Nations included an interest in other technical fields of standardization. The International Standards Organization (ISO) was set up in 1947 as a part of the UN Charter. When a sufficient number of nations agree

there is a standards problem in a certain technical area, a vote is held to establish a Technical Committee (TC) to deal with that problem. Over the years, several TC's were started that dealt with areas that depended in one way or another on optics. About the time this was beginning to be a jurisdictional problem, there was also a decline in the commercial optics business in the U.S., along with simultaneous growth in the optics industry in Europe and Asia. This meant that U.S. optical drawings, complete with copious notes, had to be translated into the native language of the country making the optics. This added substantially to the overhead of making the optics. In 1979, a new TC was established to deal with optics problems in a unified manner. This new TC was ISO/TC172-0ptics and optical instruments. Within TC172 there are 9 subcommittees (SC's) dealing with various aspects of the field. The SC responsible for ISO 10110 was SCl, Fundamental standards. SCl has 3 working groups and ISO 10110 was written by WG2, Optical drawings. The other WG's are WGl, Optical testing, and WG3, Environmental testing. The delegates to ISO/TC172/SC1/WG2 began work in 1979 on a standard called Indications in optical drawings, the document now given the designation ISO 10110. Several cultural matters influenced the contents of this document. While these are not technical matters, they do help to explain some aspects of the standard that make it appear unusual at first glance. We feel that if the reasons for these unusual appearances are explained up front, the standard will take on a greater degree of acceptance than if these appearances are ignored or overlooked. One thing that is immediately obvious to workers in the field is that ISO 10110 looks much like, or has the flavor of, the German DIN 3140 optical drawing standard. This comes about because the Germans were very instrumental in starting ISO/TC172, and they had a voluntary national optical drawing standard that dates from at least 1957. It is also an ISO rule that when an international standard is to be written, all of the delegates are invited to bring their OSA USER'S GUIDE FOR ISO 10110 •

1

own national standards to the table as a starting place. Since the Germans had the most thorough optical drawing standard at the time, it became the basis for what was to follow. The reasonably complete, but dated, U.S. military standards for optics could not initially be brought to the table, because, under ISO procedures, they are not voluntary national standards. While the German drawing standard became the foundation of ISO 10110, there were problems with its adoption as a whole. One problem was administrative, and the other nationalistic. The administrative problem was that German is not one of the official languages of ISO, but English, French, and Russian are. This meant that the various parts of DIN 3140 had to be translated into English (and in the early meetings of WG2, into French as well). Translating technical jargon into a non-native tongue by engineers, rather than linguists, does not necessarily lead to the most idiomatically correct English. As the various delegates worked on the technical aspects of these translated documents, certain words and phrases took on a familiar sound and they were left largely as originally translated. Besides, at the time, everyone was thinking there would be a technical editor at ISO who would take care of this, so nothing was done with the language itself, and thus, we have expressions like "Indications in drawings." To some English speaking engineers, this just barely gets the idea across that this standard shows how one expresses symbolically on optical drawings what one wants in the way of dimensions and function. This unintentional linguistic obscurity in the standard is another reason for this handbook. On the nationalistic front, many of the delegates were saying to themselves, "This isn't international, we're just adopting the DIN standard." In order that this did not happen, virtually every designation in the DIN standard was changed just enough so that it would confuse the people familiar with DIN 3140, just as much as the new ISO 10110 would confuse those people working with other national standards. The point of this is to remind the reader not to be too critical of the English or the precise logic of some parts of the standard. It was the best compromise that many very dedicated engineers could realistically put together in a limited time on a voluntary basis. It is now up to you to try to implement the standard in just as dedicated a way. If faults are found, and there is no question they will be, write them down and make the Committee aware of them so they may be corrected at the mandatory 5-year reviews of the standard. Another goal of the engineers who originally started working on the standard was to express as many concepts as possible in terms of symbols (numerical or otherwise), so as to minimize the need for notes that require translating as a drawing goes from coun-

2 •

OSA USER'S GUIDE FOR ISO 10110

try to country. The idea was that just the ISO 10110 standard itself would need to be translated into, say, Japanese. Once the shop workers understood the translated version of the standard, the symbols would mean the same thing without translation. The optical element drawing itself could then be taken from shop to shop with a reasonable expectation of getting the same optic, independent of where the part was made. The idea of using symbols has great merit, but it leads to a drawing that is much more cluttered or complex than many people are used to dealing with. This will probably be a workable situation once opticians, designers, and inspectors become familiar with the concept. Somewhat in reaction to the comments about cluttered drawings, there is a scheme for characterizing lens parameters in a tabular form in the standard, and a table of default tolerances that apply to certain features, even if they are not specified on the drawing. Both ideas minimize the information that needs to be placed on the pictorial part of the drawing. The point is that there are enough symbols that the need for notes on most drawings is unlikely. Another reason for writing this handbook is that some of the concepts or reasons for defining certain parameters were not initially obvious to the delegates writing the standard, and, thus, will not be obvious to the casual user of the standard. As a matter of human nature, people take matters they understand more seriously than those they do not. Thus, what we have attempted to do is give some of the reasoning and logic behind the methods of indicating certain features on optical drawings. The biggest single area where this comes into play is with "surface imperfections" or, more familiarly, the "scratch and dig" standard. In the U.S., there is a general unhappiness with the scratch and dig standard, but no one has taken the time to search out and propose a more workable scheme. DIN had a concept for a better method but some felt the idea was taken too literally. In the process of writing ISO 10110, Part 7, a very reasonable compromise was worked out, and now we will have to see how it works in practice. One of the consequences of this is that not only will the U.S. Army be able to make "official" scratches, but anyone the world over will be able to make reproducible scratch artifacts and relate them to the Army standard. There is also a quantitative method of settling differences over particular scratch designations during inspection, and a method of specifying imperfections based entirely on their visibility if cosmetics is of primary concern. Unfortunately, there is no place to go within the body of the standard for details about these matters. On the other hand, unless the engineers who use the standard understand the thinking behind these concepts, they will not be used at all, or will be used incorrectly. Finally, we want to address a subject that has noth-

ing to do with the interpretation of the standard, but is just as important a subject, how to implement a new standard that is unfamiliar to almost everyone who will be required to use it, from the optical designer to the inspector. We had not seriously thought about the mechanism for introducing the new standard into the industry until an engineer called one day and said, "Look, we have never done optical drawings, so we are starting with a clean slate. Now that we do have to produce some drawings, should we start using this new international standard instead of learning something that will soon be obsolete?" Many of us think ISO 10110 is a vast improvement over the current state of affairs, but we have to be honest, and say, that if this engineer did drawings according to the new standard, very few shops would understand the drawings and the optics would either end up costing more than they should or would not function as expected. After giving this some thought, we suggested that current practice be used until some feature was found that could not be adequately expressed using the current scheme. For that feature , the appropriate part of the new ISO 10110 should be used and a copy of the standard sent along with the request for quotation. If everyone adopted this same approach to introducing the new standard, it would be used most in those cases where current practice is not adequate. Then adoption of the new standard would be technically, rather than bureaucratically, driven. As more people become familiar with the new standard, more

parts of it will become standard practice until the entire standard is used. Even before ISO 10110 is officially adopted, we think that this is a good way to start to use it. There is a section of the standard that covers surface roughness, for example, an area where there is currently no standard method for indicating this parameter. In those areas of optical technology where it is necessary to call out surface roughness, the new standard will be immediately useful. Another part deals with specifying surface figure as measured with a phase measuring interferometer, again an area where the technology has moved so quickly that there is no commonly accepted approach. As designers, opticians, and inspectors have to look at one part of the standard, they are bound to familiarize themselves with the other parts and the adoption of the new standard will grow. Those persons and companies that are reluctant to use the new standard will soon find that they cannot do business without making use of ISO 10110. In the end, the purpose of this handbook is to make it easier for you to use the new optical drawing standard, ISO 10110. We recognize that neither the standard, nor this handbook, are perfect, and that we can benefit from the experiences of those of you who use it. It is the purpose of the Optical Society's Standards Committee to foster mutual understanding in the areas of optical standards and we welcome your comments and suggestions for improvements in the handbook and the standard. The OSA Standards Committee

OSA USER'S GUIDE FOR ISO 10110 •

3

CHAPTER 1

General

This chapter reflects Part 1 of 13 parts of ISO 10110 Optics and Optical Instruments-Preparation of drawings for optical elements and systems. This standard was generated by ISO Working Group 2 (WG2) of Subcommittee 1 (SCI) of Technical Committee 172 (TC 172). The goal of this standard is to create universally understood drawings and specifications as the basis for international manufacture and inspection of optical products to facilitate worldwide trade. For this reason, ISO uses codes and symbols extensively, rather than descriptive notes that require translation into one or more languages. Although ISO mechanical drawing practices are often applied, many drawing indications are unique to optical parts. Some interpretations of mechanical indications used in ISO 10110 are in direct conflict with ISO mechanical standards and should be used with caution. These conflicts will be identified in the appropriate chapters of this handbook. Clarifying notes are still permissible beyond the choice of (usually) several specification methods. ISO 10110 describes the rules for formatting drawings and tolerancing the mechanical dimensions of optical elements and systems. Detailed descriptions of codes and symbols are contained in Parts 2-13 of ISO 10110. 1.1 BACKGROUND

The optical industry has its roots in Europe, particularly in Germany and England. The technology was imported to the U.S. in the middle of the nineteenth century when several of the well known optical companies were established. More recently, Japan and other Asian countries have become volume producers of optics. Standardization started during World War II, as many of the U.S. military standards attest. Perhaps the most comprehensive optical standards are found in Germany as "Deutsche Industrie Normen," or DIN standards. It is, therefore, not surprising that many ISO standards are based on DIN standards. However, the U.S. has made valuable contributions, particularly in the fields of interferometry, surface metrology, and lasers. In 1979 the inaugural meeting of ISO/TC172 was held, and, as a result, WG2, "Indications in optical 4 •

OSA USER'S GUIDE FOR ISO 10110

drawings" was founded on April 16, 1980. The international makeup of ISO standards working groups had to consider all prevailing practices and generate standards acceptable to all. National preferences gave way to internationally acceptable standards which are intended to reflect the best technical solutions, and sometimes represent compromises. All standards are "living documents," and can and will undergo changes as they are periodically reviewed. An example of a lens element drawing is presented in Fig. 1.1 to be used as a reference for the discussion of Part 1 of ISO 10110 that follows . 1.2 ISO 10110 INDICATIONS ON ORA WINGS

The drawing indications in this part of ISO 10110 define the mechanical dimensions and appearance of drawings of elements and systems. Section 4 of ISO 10110-1 applies to optical elements, and Section 5 applies to the optical layout drawing. The following discussion will, in general, follow the sequence of Part 1 of ISO 10110. This discussion is intended to aid both the creation and interpretation of drawings, but is not intended as a substitute for ISO 10110. The user of this handbook should have ISO 10110 available when establishing indications on drawings. Section 2 lists other standards that may be referenced in the text of Part 1. These standards are identified as "normative," which, in the European community, means mandatory, rather than reference. Practices that are not mandatory are identified as "informative." Section 3 defines fundamental concepts that apply to all optical drawings. Of particular importance to U.S. industry is the use of the metric system for linear dimensions, although the standard does allow use of the English system, which must be stated on the drawing. The use of the metric system per ANSI Y14.5M-1982 will satisfy the ISO standards, except that a comma is used in the ISO standard instead of a period for decimal indications. Section 4 describes the rules for presentation and dimensioning of optical components and subassemblies. These rules generally follow ISO 128-1982 (E)

G

3/3 (1) 4/2' 5/5x0. 16; L2x0.0~

B

E 0. 5

test volume O? (T'l

a:l

(T'l

"&.

"s)Y

(17)

Thus, equations 16 and 17 relate the absolute intensity and angular distribution of scattered light to the power spectral density function and to the surface spatial frequency and, thus, give a complete description of the scattering in terms of intrinsic surface properties. In order to calculate the scattering into a 2-dimensional area in an image plane, one needs to compute the 2-dimensional PSD function for the surface from measurements of the surface topography over a finite area on the surface. If the surface roughness is isotropic, i.e., the roughness parameters are the same regardless of direction on the surface, we can reduce the problem to a one-dimensional measurement and calculation. If the surface is random and isotropic, 60 •

OSA USER'S GUIDE FOR ISO 10110

the 2-D power spectrum is related to the 1-D spectrum by an integral transform (see Ref. 10): (18) where f = jfj. As an example, for an isotropically rough fractal surface with a 1-D power law spectrum given in the standard form S 1(fx) = A/f 8 , the 2-D spectrum is given by (see Ref. 18) S2 (f)

=

r[(B + 1)/2] A 2f(l/2)f(B/2). f~+ I

(

19)

As a numerical example, for the case of a surface with a 1-D inverse square power law function, B = 2, the value of the gamma function term is simply 1/4, and the form of the 2-D PSD function is just 1/4 times the 1-D function, with the exponent of the spatial frequency equal to 3 instead of 2. In most practical applications, rather than compute the 2-D power spectrum directly from the data, it is much easier to measure the profile in one dimension along several lines on the surface, compute the average 1-D power spectrum and then use the integral transform method to compute the 2-D form of the power spectrum. The practical process for estimating the 2-D spectrum is then to measure the surface topography in one dimension, compute the 1-D spectrum, fit the 1-D spectrum to the power-law model to determine the A and B coefficients, and then evaluate the f-function coefficient and spatial frequency exponent in equation 19, that are dependent upon the value of B. If the 1-D surface spectrum cannot be fit to the simple power law function, then the 2-D PSD function must be computed numerically from equation 18. 8.5 INSPECTION AND TEST The ability to specify surface texture precisely by drawing indication is important when surface texture plays a significant role in the process that ultimately needs to be controlled. For optical surfaces, that process is usually scattered light. Because of the close functional relationship between surface roughness and scattered light, there are two fundamentally different methods that have been developed to characterize surface texture. They are: 1) directly by surface profilometry, and 2) indirectly by optical scatter methods, either by total integrated scatter or by angle resolved scatter methods. Each method has its strong points and its drawbacks. What is important is that the results of the test method are meaningful to both the supplier of the parts and to the end user. The drawing indication does not, however, specify which method is to be used in measuring RMS roughness or the power spectral density function-it is up to

the manufacturer and procurer to be sure that the test methods actually used really do measure the appropriate quantity over the specified bandwidth. 8.5.1 Surface profilers-contact instruments

A recent review of instruments available for measuring surface topography can be found in the book by Bennett and Mattsson (see Ref. 17). In general, there are two classes of profiling instruments currently in common use, contact and non-cont~ct instruments. The best-known of the contact mstruments are the stylus types made by Tencor, Veeco/ Sloan, and Rank Taylor Hobson. These instruments use a shaped diamond stylus to follow the conto~r of the surface as the surface is translated under It, or vice versa. A very sensitive linear transducer, usually an LVDT, measures the vertica~ motio~ of the stylus. Instruments are available _with varymg grees of vertical sensitivity. For optical surfaces, high vertical sensitivity is always required in order to measure to the Angstrom level. Also required is a low system noise level and measurement repeatability. If the noise level is too high, the true surface roughness will be impossible to extract from the data, and if the measurement is not repeatable, the validity of the data is questionable. Software is available f.rom the manufacturers to compute most of the desired statistical parameters of the surface important for mechanical engineering purposes, such as Rq and R., but no manufacturer presently provides software to calculate the PSD from the measured data. An ASTM subcommittee, E12.09, is currently at work on a standard to define the calculation of the PSD from surface profile data. . Another type of contact profiling instrument IS the scanning probe microscope, of which there are a number of variations made by several manufacturers, such as the tunneling microscope and the atomic force microscope. These profilers allow one to approach atomic dimensions both on a vertica~ scale and on the lateral scale. The diamond stylus mstruments typically provide information on spatial periods longer than 100 nanometres, while scanning probe instruments extend that range down by two orders of magnitude to the nanometre lateral scale. It is important to realize that if one wishes to use profiling instruments to predict scattered ligh.t fr~m surfaces, the spatial bandwidth of the measunng mstrument should match, or at least partially overlap, the spatial periods that contribute to the scattering at the wavelength of interest. For instance, at normal incidence and at visible wavelengths, the shortest spatial period that contributes to scattered light (i.e. , when 65 = 90°) is approximately equal to the wavelength of the light, which is on the ord~r of~~~ fl.m. For the purpose of predicting scattered hght, It IS not necessary to extend the measurement range to spatial

?e-

periods much below this value. Diamond stylus p~o­ filers match the bandwidth required for normal mcidence visible scattering very closely, while the scanning probe microscopes provide lateral resolution far beyond the cutoff frequency for visible light scatter. If, however, one desires to reflect x-rays from a normal incidence multilayer coating, one needs to extend the lateral resolution down to the nanometre region, necessitating the use of a scanning probe instrument. 8.5.2 Surface profilers-non-contact instruments

The other class of surface profiler is the non-contact instrument, of which the most common are based upon various kinds of optical probes. The most prevalent type of optical profiler is the micro phase-measuring interferometer (micro PMI), which consists of a microscope with a interferometric objective, a means to modulate the distance between the objective and the test surface, and a linear or area array detector. A selection of micro PMI instruments for surface profilometry are available from a number of manufacturers, such as WYKO, Zygo, Micromap, and Phase Shift Technology. Micro PMI profilers are available with a range of objective magnifications, but are constrained to a high spatial frequency limit by the wavelength of the source illumination and the n~merical aperture of the objective, which for practical p~r­ poses is the illumination wavelength. The low spatial frequencies are limited only by the total length of the trace, which, for 1,5x magnification objectives, is about 8 mm. In addition to micro PMI profiling systems, other kinds of optical systems with subnanometre resolution are available for surface topography measurement. These usually entail scanning a focused spot across a surface and measuring the phase shift between the probe and reference beams by Nomarski techniques or by various heterodyne techniques. Scanning spot profilers are available from Chap~an Instruments, Bauer Associates, Optra, and Cranfield Precision Engineering, among others. The Bauer instrument is rather unique, in that it measures surface "curvature" directly, rather than surface height or slope, as do the other instruments. Another class of non-contact scanning optical profiler is the pencilbeam type, of which the Long Trace Profiler (LTP II) manufactured by Continental Optical Corporation is the most widely known. A particularly useful characteristic of scanning profilers is that they are capable of measuring over long traverse lengths. The Chapman instrument has a typical scan range of 100 mm, while the LTP II is capable of 1 or 2 metre long measurements. 8.5.3 Scattered light measuring instruments

The other method of surface texture characterization is by scattered light measurement, of which there are two main methodologies. These are total inteOSA USER'S GUIDE FOR ISO 10110 •

61

grated scatter (TIS) methods and angle-resolved scatter (ARS) methods. TIS measures the ratio of the total amount of light scattered into a hemisphere from a region on a surface relative to the incident beam intensity. The quantity of interest to the surface texture drawing indication is derived from the measured TIS by solving equation 15 for the RMS roughness, Kr One must always be alert to the fact that other factors may contribute to the measured TIS in addition to surface roughness, for example, particulate contamination, solvent residue or differential phase retardance due to position-dependent optical constants, so that the Rq number derived from equation 15 may be larger than the true RDMQ6c RaUfanl'eJo(thU aamplc wu ruled a. •hown. F1~&m« ~rK"a•urcrrwrttpreeUtcws ucuplw or min.ru J~ ,__,elo NIST. 1'he ,_., tMIMd ua• eubet.arttiaU_v in ~~willa ISO 11%54. Sp«'iftt! «JlDuDon dal4 arw ~itt ~off&« tuttl arc owsiltJhl. for U..ee'*'". Otttoi.Ud &.eriptiolu o(tlw tal Cla'JIIOI"Dtu OIStl ~ ~ Gnt ouailGblc Gft reoMOt.

_ _ __,lASER DAMAGE TESTING_ _ __

FIG. 13.4.

Typical durability certification.

OSA USER'S GUIDE FOR ISO 10110 •

83

Glossary for ISO 1 011 0

This glossary of terms is taken from ISO 10110, Optics and optical instruments-Preparation of drawings for optical elements and systems, but is not part of that standard or any other standard, and is not, of itself, a standard. The definitions are taken from ISO 10110, verbatim where possible. These definitions are not approved outside the context of ISO 10110, but were written by the Standards Committee of the Optical Society of America as a general reference for use with the User's Guide to ISO 10110 that was edited by Standards Committee members. Applicable chapters of ISO 10110 and the User's Guide are given iil parentheses after the definition. All 0: The size of the sub-aperture (test field) over which the surface form tolerances apply. (5) Approximating Aspheric Surface (AAS): The least squares fit of a series of rotationally symmetric Zernike polynomials to the irregularity function. (5)

Bevel: A functional surface replacing a sharp edge, that must be completely specified with respect to dimension, tolerance, inclination, and, if necessary, centring. (1) Bubble: Gaseous voids in the bulk material of generally circular cross section that sometimes appear in glass as a result of the manufacturing process. (3)

Centring error: A centring error exists when an optically effective surface is not perpendicular to the datum axis at the intersection point. (6) Clustering: A concentration of imperfections within the bulk material or on a surface. (See also concentration.) (3) Coating Blemishes: Coating imperfections, such as grey spots and color sites that absorb or reflect light differently from the bulk of the coating. (9) Concentration: A grouping of material defects or surface imperfections that occur within a specified part of the test region. (3, 7) Conic Surface: A rotationally symmetric surface obtained by rotating a conic section about its axis. (12) 84 • OSA USER'S GUIDE FOR ISO 10110

Datum Axis: A reference axis used to locate surfaces, elements, and assemblies. (6) Datum Feature: A readily discernible feature of a part that has a datum as its geometric counterpart. (6) Datum Point: A specified point on the datum axis used as an additional reference to the location of an optical system. (6) Decentration: The distance between the optical axis and the mechanical axis of a lens element. (6) Deflection Angle: For a prism, the angle between the incident and emergent rays. (6) Deutsche Industrie Normen (DIN): German standards written after World War II on which several of the ISO standards are based. (1) Deviation: The angle between an incident ray directed along the mechanical axis of a lens and the emergent ray. (6) Digital Interferometer: An interferometer that uses digital analysis to determine the various types of surface form error. (5) Drawing Field: The part of a drawing using tabular indications that contain the pictorial and mechanical dimensions of an element. (10) Edge Chips: Localized defects around the periphery of an element. (7) Edge Roll: A surface form error that lies within the outer 10% of the dimension of an optical surface. (5)

Edge Runout: The mechanical runout of the edge of a lens element when the lens is rotated about its optical axis. (6) Effective Diameter 0e: The [circular] region of the optical surface to which the tolerances apply; clear aperture; free aperture. (1) Fringe Spacing: The unit for indicating surface form deviation. One fringe spacing is equal to a distance equal to one half the specified light wavelength. (5)

Full Indicator Movement (FIM): The total movement of an indicator when appropriately applied to a surface to measure its variation. (6) Grade Number: When applied to surface imperfections, the grade number is the square root of the

surface area of the maximum allowed defect in millimetres. (7) Image Runout: The runout of the image of a collimated input beam when a lens is rotated on its outside diameter. (6) Inclusion: All localized bulk material defects other than bubbles. Includes striae knots, small stones, sand and crystals. (3) Indication: Numbers, letters, and symbols used on the face of the drawing to define tolerances. (1) Inhomogeneity: A gradual variation of refractive index within an optical element. (4) Irregularity: The Peak-to-Valley departure of a surface from the best fit spherical surface. (5) Irregularity Function: The difference between the total surface deviation function and the best fit sphere. (5)

Laser Irradiation Damage Threshold: The level of energy density or power density below which surface damage shall not occur when the surface is irradiated by a pulsed or continuous laser. (13) Long Scratch: A thin surface imperfection longer than 2 mm. (7) Matte Surface: A surface that has height variations of the surface texture that are not considerably smaller than the wavelength of visible light. (8) Micro-defect: Small irregularities, generally less than 1 micrometre in size, in a specular surface, usually pits remaining after an incomplete polish, that are reasonably evenly distributed over the surface. (8) Normative: When applied to a standard, means mandatory, i.e., the provisions of that standard must be used. Practices that are not mandatory are informative . (1) Optical Axis: The theoretical axis about which the optical system is normally rotationally symmetric. (6)

Optical System: A generic term used in ISO 10110-6 to refer to an optical element, sub-assembly, or assembly. (6) Optically Effective Surface: A surface with optical function. (1) Peak-to-Valley: The maximum distance minus the minimum distance between two surfaces. (5) Polishing Grade: A grade number used to indicate the allowed number of micro-defects. (8) Power: When applied to surface form deviation of nominally plane or spherical surfaces, the maximum departure of a test surface from the theoretical surface. (5) Power Spectral Density Function (PSD): A means of indicating the roughness of a surface as a function of the surface spatial period. (8) Protective Chamfer: A small surface replacing an edge or corner, approximately equally inclined to the surface forming the edge or corner. (1) Pulse Repetition Rate: The number of pulses per second of a pulsed laser. (13)

Reference Wavelength: 546,07 nm at a temperature of 22 ± 2°C. (1, 5) RMS: Root mean square. (5, 8) RMSa: The RMS departure of the test surface from the best fit aspheric surface. (5) RMSi: The RMS departure of the test surface from the best fit spherical surface. (5) RMSt: The RMS departure of the test surface from a sphere with the nominal radius of curvature. (5) RMS Surface Roughness: The RMS of the height variations of a surface from an average surface. (8) Rotationally Symmetric Irregularity: The Peak-toValley of the best fit aspheric surface. (5) Sagitta Error: The Peak-to-Valley deviation of the best fit sphere from the nominal (theoretical) radius of curvature. (5) Scale Comparison Plate: A plate containing artifacts that may be used to compare surface defects to determine conformance to surface imperfection specification. (7) Slope Error: The local deviation of the surface normal from the nominal value. (12) Specular Surface: A surface is specular if the height variation of the surface texture is considerably smaller than the wavelength of visible light. (8) Stress Birefringence: Birefringence due to residual stress within a glass blank due to forming, annealing, or manufacturing process. (2) Striae: Inhomogeneities of small spatial extent within the bulk material that are easily observed by visual tests. (4) Sub-system: Part of a system. (6) Surface Form Deviation: The difference between an optical surface under test and the nominal theoretical surface. Commonly called figure error in the U.S. (5) Surface Imperfection: A localized defect within the optically effective aperture of an optical surface produced by improper treatment during or after the fabrication process. (7) Surface Texture: A global characteristic of optical surfaces exclusive of surface imperfections. (8) Surface Treatment: A functional thin film coating applied to an optical surface or a protective coating applied to optical or non-optically effective surfaces. (9) Table Field: The part of a drawing using tabular indications that contains tolerance indications. (10) Test Field: An area within a test region, usually circular, indicated with requirements applicable to all possible positions of the test field within the test region. (1, 5) Test Region: The region of a surface to which the optical specifications apply, indicated by boundary lines and shaded. A test region may be divided into zones. (1) Test Volume: An indicated volume of a component OSA USER'S GUIDE FOR ISO 10110 •

85

that must fulfill higher requirements than the rest of the optical element. (1) Title Field: The part of a drawing using tabular indications that provides general indications not required by other parts of ISO 10110. (10) Torroidal Surface: A surface generated by the rotation of a defining (circular) arc about an axis that lies in the plane of this arc. (12) Total Indicated Runout: A term used erroneously to describe Total Indicator Runout. (6) Total Indicator Runout (TIR): The terminology formerly used for Full Indicator Movement. (6) Total Surface Deviation Function (TSD): In digital

86 •

OSA USER'S GUIDE FOR ISO 10110

interferogram analysis, the residual after subtracting the best fit plane from the measured wavefront error. (5) Visibility Method: When applied to surface imperfections, a method of specification of surface imperfections that requires the use of a specific test station to verify conformance to drawing specifications. (7) Visibility Class: An indication that specifies the level of illumination for visibility tests for surface imperfections. (7) Witness Substrate: A substrate coated along with an optical element that is used for spectral and durability tests. (9)