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Principles of optics (5th Edition)
BOOKS Holographic
non-destructive
testing
Edited by R. K. Erf Academic Press (New York, London) g14.00, $28.00
1974, pp 462,
This book sets out, according to the dust-jacket, to give ‘a comprehensive description of holographic non-destructive testing, - from the underlying mathematical theory to the specific experimental techniques’, ‘to provide sufficient engineering detail to enable the reader to assemble equipment and perform holographic tests’, and to include ‘the sophisticated mathematics necessary for a c;mplete understanding of the methods’. In some of these aims it succeeds very well; it gathers together-; very large amount of information on HNDT up to about 1971/2. As might be expected from a collection of contributions by different authors (all but two are American) there is a certain amount of repetition, and the style and level of approach varies considerably. It is excellent as a book for browsing through, for getting an idea of the possibilities, and, to a large extent, for acquiring information on setting-up test equipment. It is much less effective, however, in its coverage of the underlying theory and in giving a ‘complete understanding of the methods’. In particular, a large part of Chapter 2, intended to give the basic principles of holography, is poor. It abounds in confusing and, in some cases, incorrect statements and should be read with considerable caution. The sections on ‘Coherence requirements’ (oddly placed as sub-sections of ‘Leith-Upatnieks holograms’) and ‘Experimental Techniques’ are especially bad. Indeed, the whole concept of spatial coherence seems imperfectly understood - one comes across such phrases as ‘spatial coherence, a measure of the uniformity in the phase of a wavefront’ and ‘if the phase is random . . . the source is said to have poor spatial coherence’. Statements such as ‘the spatial coherence requirements of the source used for making LeithUpatnieks holograms is (sic) not as critical [as what is not clear] . . . . Indeed, there are no spatial coherence requirements for the object beam’ can only confuse the reader. Much of the ‘General theoretical analysis’ quotes mathematical expressions without full explanation of the symbols and, perhaps more importantly, without stating what assumptions have been made. In the zone-plate model of hologram formation used to discuss image-plane holograms, it is implied that the small chromatic dispersion obtained in reconstruction is due to large fringe spacing in the zoneplates, whereas, of course, it would be more correct to refer to small fringe spacing and the consequent very short focal length of the ring pattern. The grouping of holograms into different types leads to some oddities; eg ‘white light holograms’ refers only to those recorded on thick emulsions using the Bragg effect, yet it is noted that ‘imageplane holograms’ can also be reconstructed in white light. The general description’ of experimental techniques is by far the best part of the chapter, although there are errors: vibration-isolation is not as difficult as it sounds here; argon
190
lasers with etalons give many metres coherence length, not a few centimetres as implied; and the optimum beam ratio is not generally 1: 1. Also it is not true, as suggested at the end of the chapter, that the fringes obtained in holographic interferometry are generally located so far from the surface of the object that it is necessary to stop a recording camera down (to the point where definition is completely lost due to speckle) in order to achieve an adequate depth of field. There are similarly dubious statements in other parts of the book, eg in the section on double-exposure holography (page 90) it is stated that ‘the interference pattern which results (from the two recorded states of the object) is identical to a pattern obtained from a conventional interferometer’. This is not true except to a rough approximation. On page 232, the concepts of spatial frequency spectra seem to be inadequately understood judging by the explanation given for local reference beam generation. In places a good deal of specialist knowledge is required of the reader; for example in the chapter on holographic correlation. Here and elsewhere terms are used without reference or explanation - ‘focus condition’ (page 20), ‘aliasing moire’ (page 118), ‘mixed integration or incoherent summation’ (page 132) - to quote a few. Careless writing makes uncomfortable reading, at least for this reviewer - foci and phenomena repeatedly used as singular nouns, alternate where alternative is meant, a ‘highvoltage (60 W) bulb’, and many others. Since the same system is used for numbering sections, figures, and references it is sometimes difficult to know which is meant. Tighter control by the editor in relating chapters and avoiding unnecessary duplication, (eg a paragraph describing basic principles is given on page 235 as well as at the beginning of the book), and provision of a much more comprehensive index, would improve the book considerably. It is very well produced, however; the diagrams and photographs are of high quality and I found few typographical errors. In spite of its shortcomings it should undoubtedly find a place in the range of books on holography as well as those on non-destructive testing. It introduces the ever-increasing range of NDT applications, often in a practical and realistic way, and gives considerable guidance to anyone contemplating setting-up test equipment. The book has much to offer and, provided that the detailed explanations are read with due caution, it can be recommended as an introduction to, and summary of. HNDT for non-specialists in the field of optics. M. Marchan t Principles of optics (5th Edition) M. Born, E. Wolf Pergamon Press, Oxford, 1975, pp xxviii + 808, E9.50 Since the first edition of this book was published in 1959 it has become a classic and a standard reference on a wide range of topics in theoretical optics. The book was written, as explained in the preface to the first edition, as a presentation of those parts of optical theory which can be derived
OPTICS AND LASER TECHNOLOGY.
AUGUST
1975
from Maxwell’s equations of the electromagnetic field; this is taken to include geometrical optics, although it is d!fficult to produce a simple, complete, and rigorous formulation of the transition from wave theory to geometrical optics. For the rest, the book covers thin film theory, properties of materials media, interference, diffraction, coherence theory, and the optics of metals and of crystals. There are good author and subject indexes, and several appendices dealing with points of mathematical detail. The restriction to results which follow from Maxwell’s equations means that many topics which one would expect to find in a conventional optics text of this size do not appear at all, or are treated; very briefly, eg emission and absorption of light, lasers, and nonlinear effects. Nevertheless, ‘Principles of optics’ occupies a very special place in the literature of optics; this is because it comes as near as is conceivable to being a perfectly written textbook. By this I do not merely mean that it is free from errors and misprints, although the few that were in the first edition have been steadily reduced as the editions progress, but that the writing has a combination of clarity and scholarship comparable to that of, say, E. T. Whittaker. All mathematical and physical arguments are developed with great elegance and with full historical references, and the book is a pleasure to read. ‘Principles of optics’ is essentially a theoretical book and it is mostly at postgraduate level. The reader cannot learn thin film design from it, or how to use an interferometer, or how to make an ultrasonic diffraction grating, but the principles behind all these things and many more are explained. Thus the book is to be regarded as a source of basic theory for the optics specialist at postgraduate and research level. The book has increased in length by only seven pages since the first edition, two of these being in the preliminaries. Thus it seems that the policy of the surviving author is not to attempt to update the book to take account of recent developments. If this were to be done it would mainly affect the choice of applications which are described as examples of the basic theory; eg the Lummer-Gehrke plate and the Michelson echelon grating are no longer used and could perhaps give place to an expanded treatment of holography. Some discussion of the statistics of coherent light speckle would also be useful, and optical resonators would provide good example material at either geometrical or wave optics level. However, it appears to me that Professor Wolfs implied choice is right, to leave the book substantially as published in 1959. The presentation of basic theory will probably remain the best available in English for many years to come. The book is beautifully produced and at just over 1p a page it is good value. It can be recommended without reserve as one that every serious worker in optics should have on his bookshelf. W. T. Welford Developments
in laser technology
-
II
Edited by R. F. Wuerker Proceedings of the Society of Photo-Optical Instrumenta17th Annual Technical Meeting, 1973) 29.00
OPTICS AND LASER TECHNOLOGY,
AUGUST
1975
What do measurements of the lunar orbit to an accuracy of 10 cm, the removal of surface encrustations on a small marble gargoyle from the Loggetta de1 Campanile di San Marco, novel techniques of chromosome dissection and bloodless surgery, and controlled thermonuclear microexplosions have in common? Readers of this journal will doubtless recognize in each of these activities a recent development in laser technology - a subject which was chosen for a seminar-in-depth at the 17th Annual Technical Meeting of the Society of Photo-Optical Instrumentation Engineers, San Diego, 27-29 August, 1973. The proceedings of this meeting comprise 3 1 abstracts and papers covering an extraordinarily wide field of applications; some question-and-answer sessions are also reproduced. This reviewer felt that the quality of the individual papers was equally wide. The treatment ranged from a 12 page theoretical monograph on ‘Laser internal aerodynamics and beam quality’ (Biblarz and Fuhs), through quantitative state of the art experimental papers on such subjects as laser driven fusion (Brueckner) and electronbeam laser pumps (Maxwell Laboratories), to qualitative one or two page abstracts on ‘Molecular association lasers’ (Bhaumik and Ault) and ‘Integrated optics’ (Barnoski and Evtuhov). Perhaps this unevenness of treatment is inevitable in a volume which also encompasses seven papers on medical or dental applications of lasers, a history of American military funding in fundamental laser research, a summary of various techniques for generating holograms by means of a digital computer and associated display devices, and a survey of the uses of He-Ne lasers in the construction and building industries. The sheer variety of subject matter provides the major attraction of the book. If you are interested in a laser cane for the blind - capable of providing simultaneous audible warnings of any drop in ground level greater than 13 cm, and of any obstructions either straight ahead or at head height - then you should read the article by Benjamin and Ali. Prognostications for the potential of the laser in medicine and dentistry are discussed by Goldman and by Stern, respectively. Practical applications of holography are treated in several experimental papers. These include a remarkable photograph of the improved image which can be obtained by holographic reconstruction of an object obscured in moving fog (Shuman) and a fascinating discussion of developments in tine holography for the study of marine plankton in the laboratory and, hopefully, in the sea (Stewart, Beers, and Knox). A related paper from the Scripps Institution of Oceanography discusses problems of under-water illumination. Who, then, might wish to purchase a (soft-back) volume which, to non-members of SPIE, costs some $29? Clearly the book provides a convenient reference work for those who were directly involved in the seminar, and it may also be purchased by a few of the more adventurous laser libraries. For the rest, it will be of use to those in industry or universities who are interested in the sheer diversity of laser applications and technology. It seems much less likely to be purchased by the specialist in, say, high power (1 Or 1- lOr*W) laser design, or length digitization to accuracies of parts in 10 r2-10r4, although there are excellent articles from the Naval Research Laboratory and Sandia Laboratories on these two topics. L Spurding
191
non-destructive
testing
Edited by R. K. Erf Academic Press (New York, London) g14.00, $28.00
1974, pp 462,
This book sets out, according to the dust-jacket, to give ‘a comprehensive description of holographic non-destructive testing, - from the underlying mathematical theory to the specific experimental techniques’, ‘to provide sufficient engineering detail to enable the reader to assemble equipment and perform holographic tests’, and to include ‘the sophisticated mathematics necessary for a c;mplete understanding of the methods’. In some of these aims it succeeds very well; it gathers together-; very large amount of information on HNDT up to about 1971/2. As might be expected from a collection of contributions by different authors (all but two are American) there is a certain amount of repetition, and the style and level of approach varies considerably. It is excellent as a book for browsing through, for getting an idea of the possibilities, and, to a large extent, for acquiring information on setting-up test equipment. It is much less effective, however, in its coverage of the underlying theory and in giving a ‘complete understanding of the methods’. In particular, a large part of Chapter 2, intended to give the basic principles of holography, is poor. It abounds in confusing and, in some cases, incorrect statements and should be read with considerable caution. The sections on ‘Coherence requirements’ (oddly placed as sub-sections of ‘Leith-Upatnieks holograms’) and ‘Experimental Techniques’ are especially bad. Indeed, the whole concept of spatial coherence seems imperfectly understood - one comes across such phrases as ‘spatial coherence, a measure of the uniformity in the phase of a wavefront’ and ‘if the phase is random . . . the source is said to have poor spatial coherence’. Statements such as ‘the spatial coherence requirements of the source used for making LeithUpatnieks holograms is (sic) not as critical [as what is not clear] . . . . Indeed, there are no spatial coherence requirements for the object beam’ can only confuse the reader. Much of the ‘General theoretical analysis’ quotes mathematical expressions without full explanation of the symbols and, perhaps more importantly, without stating what assumptions have been made. In the zone-plate model of hologram formation used to discuss image-plane holograms, it is implied that the small chromatic dispersion obtained in reconstruction is due to large fringe spacing in the zoneplates, whereas, of course, it would be more correct to refer to small fringe spacing and the consequent very short focal length of the ring pattern. The grouping of holograms into different types leads to some oddities; eg ‘white light holograms’ refers only to those recorded on thick emulsions using the Bragg effect, yet it is noted that ‘imageplane holograms’ can also be reconstructed in white light. The general description’ of experimental techniques is by far the best part of the chapter, although there are errors: vibration-isolation is not as difficult as it sounds here; argon
190
lasers with etalons give many metres coherence length, not a few centimetres as implied; and the optimum beam ratio is not generally 1: 1. Also it is not true, as suggested at the end of the chapter, that the fringes obtained in holographic interferometry are generally located so far from the surface of the object that it is necessary to stop a recording camera down (to the point where definition is completely lost due to speckle) in order to achieve an adequate depth of field. There are similarly dubious statements in other parts of the book, eg in the section on double-exposure holography (page 90) it is stated that ‘the interference pattern which results (from the two recorded states of the object) is identical to a pattern obtained from a conventional interferometer’. This is not true except to a rough approximation. On page 232, the concepts of spatial frequency spectra seem to be inadequately understood judging by the explanation given for local reference beam generation. In places a good deal of specialist knowledge is required of the reader; for example in the chapter on holographic correlation. Here and elsewhere terms are used without reference or explanation - ‘focus condition’ (page 20), ‘aliasing moire’ (page 118), ‘mixed integration or incoherent summation’ (page 132) - to quote a few. Careless writing makes uncomfortable reading, at least for this reviewer - foci and phenomena repeatedly used as singular nouns, alternate where alternative is meant, a ‘highvoltage (60 W) bulb’, and many others. Since the same system is used for numbering sections, figures, and references it is sometimes difficult to know which is meant. Tighter control by the editor in relating chapters and avoiding unnecessary duplication, (eg a paragraph describing basic principles is given on page 235 as well as at the beginning of the book), and provision of a much more comprehensive index, would improve the book considerably. It is very well produced, however; the diagrams and photographs are of high quality and I found few typographical errors. In spite of its shortcomings it should undoubtedly find a place in the range of books on holography as well as those on non-destructive testing. It introduces the ever-increasing range of NDT applications, often in a practical and realistic way, and gives considerable guidance to anyone contemplating setting-up test equipment. The book has much to offer and, provided that the detailed explanations are read with due caution, it can be recommended as an introduction to, and summary of. HNDT for non-specialists in the field of optics. M. Marchan t Principles of optics (5th Edition) M. Born, E. Wolf Pergamon Press, Oxford, 1975, pp xxviii + 808, E9.50 Since the first edition of this book was published in 1959 it has become a classic and a standard reference on a wide range of topics in theoretical optics. The book was written, as explained in the preface to the first edition, as a presentation of those parts of optical theory which can be derived
OPTICS AND LASER TECHNOLOGY.
AUGUST
1975
from Maxwell’s equations of the electromagnetic field; this is taken to include geometrical optics, although it is d!fficult to produce a simple, complete, and rigorous formulation of the transition from wave theory to geometrical optics. For the rest, the book covers thin film theory, properties of materials media, interference, diffraction, coherence theory, and the optics of metals and of crystals. There are good author and subject indexes, and several appendices dealing with points of mathematical detail. The restriction to results which follow from Maxwell’s equations means that many topics which one would expect to find in a conventional optics text of this size do not appear at all, or are treated; very briefly, eg emission and absorption of light, lasers, and nonlinear effects. Nevertheless, ‘Principles of optics’ occupies a very special place in the literature of optics; this is because it comes as near as is conceivable to being a perfectly written textbook. By this I do not merely mean that it is free from errors and misprints, although the few that were in the first edition have been steadily reduced as the editions progress, but that the writing has a combination of clarity and scholarship comparable to that of, say, E. T. Whittaker. All mathematical and physical arguments are developed with great elegance and with full historical references, and the book is a pleasure to read. ‘Principles of optics’ is essentially a theoretical book and it is mostly at postgraduate level. The reader cannot learn thin film design from it, or how to use an interferometer, or how to make an ultrasonic diffraction grating, but the principles behind all these things and many more are explained. Thus the book is to be regarded as a source of basic theory for the optics specialist at postgraduate and research level. The book has increased in length by only seven pages since the first edition, two of these being in the preliminaries. Thus it seems that the policy of the surviving author is not to attempt to update the book to take account of recent developments. If this were to be done it would mainly affect the choice of applications which are described as examples of the basic theory; eg the Lummer-Gehrke plate and the Michelson echelon grating are no longer used and could perhaps give place to an expanded treatment of holography. Some discussion of the statistics of coherent light speckle would also be useful, and optical resonators would provide good example material at either geometrical or wave optics level. However, it appears to me that Professor Wolfs implied choice is right, to leave the book substantially as published in 1959. The presentation of basic theory will probably remain the best available in English for many years to come. The book is beautifully produced and at just over 1p a page it is good value. It can be recommended without reserve as one that every serious worker in optics should have on his bookshelf. W. T. Welford Developments
in laser technology
-
II
Edited by R. F. Wuerker Proceedings of the Society of Photo-Optical Instrumenta17th Annual Technical Meeting, 1973) 29.00
OPTICS AND LASER TECHNOLOGY,
AUGUST
1975
What do measurements of the lunar orbit to an accuracy of 10 cm, the removal of surface encrustations on a small marble gargoyle from the Loggetta de1 Campanile di San Marco, novel techniques of chromosome dissection and bloodless surgery, and controlled thermonuclear microexplosions have in common? Readers of this journal will doubtless recognize in each of these activities a recent development in laser technology - a subject which was chosen for a seminar-in-depth at the 17th Annual Technical Meeting of the Society of Photo-Optical Instrumentation Engineers, San Diego, 27-29 August, 1973. The proceedings of this meeting comprise 3 1 abstracts and papers covering an extraordinarily wide field of applications; some question-and-answer sessions are also reproduced. This reviewer felt that the quality of the individual papers was equally wide. The treatment ranged from a 12 page theoretical monograph on ‘Laser internal aerodynamics and beam quality’ (Biblarz and Fuhs), through quantitative state of the art experimental papers on such subjects as laser driven fusion (Brueckner) and electronbeam laser pumps (Maxwell Laboratories), to qualitative one or two page abstracts on ‘Molecular association lasers’ (Bhaumik and Ault) and ‘Integrated optics’ (Barnoski and Evtuhov). Perhaps this unevenness of treatment is inevitable in a volume which also encompasses seven papers on medical or dental applications of lasers, a history of American military funding in fundamental laser research, a summary of various techniques for generating holograms by means of a digital computer and associated display devices, and a survey of the uses of He-Ne lasers in the construction and building industries. The sheer variety of subject matter provides the major attraction of the book. If you are interested in a laser cane for the blind - capable of providing simultaneous audible warnings of any drop in ground level greater than 13 cm, and of any obstructions either straight ahead or at head height - then you should read the article by Benjamin and Ali. Prognostications for the potential of the laser in medicine and dentistry are discussed by Goldman and by Stern, respectively. Practical applications of holography are treated in several experimental papers. These include a remarkable photograph of the improved image which can be obtained by holographic reconstruction of an object obscured in moving fog (Shuman) and a fascinating discussion of developments in tine holography for the study of marine plankton in the laboratory and, hopefully, in the sea (Stewart, Beers, and Knox). A related paper from the Scripps Institution of Oceanography discusses problems of under-water illumination. Who, then, might wish to purchase a (soft-back) volume which, to non-members of SPIE, costs some $29? Clearly the book provides a convenient reference work for those who were directly involved in the seminar, and it may also be purchased by a few of the more adventurous laser libraries. For the rest, it will be of use to those in industry or universities who are interested in the sheer diversity of laser applications and technology. It seems much less likely to be purchased by the specialist in, say, high power (1 Or 1- lOr*W) laser design, or length digitization to accuracies of parts in 10 r2-10r4, although there are excellent articles from the Naval Research Laboratory and Sandia Laboratories on these two topics. L Spurding
191