Multiple‐beam interference microscopy of metals by S. Tolansky

The author states in the preface that 'multiple beam interferometry is both an elegant optical technique and at the same time a valuable technological tool'. Furthermore, he says that its elegance is to be found in its very real economy of means. He then sets out to verify these premises with a detectable enthusiasm. The book consists of 13 chapters but may be divided into three areas of concern: theory, chapters 1 and 2; technique, chapters 3 to 8; and applications, chapters 9 to 13. The theory is straightforward and adequately covered for the incident illumination case. The section on technique is, in my opinion, the high point of the book. The author emphasizes that the book contains the 'know-how' resulting from years of study; this is ably demonstrated in these chapters. The heart of the multiple-beam interferometer is an optical flat on which a thin reflecting film has been deposited. The preparation and properties of several types of thin films are described in detail in chapter 3. In this chapter, the use of H~O; (20 vols) is recommended for cleaning the optical flat prior to coating with the thin film. A statement should have been included for the benefit of the technician with regard to the hazards involved in the use of this compound. Materials suitable for use as the optical flat are discussed in chapter 5. The recommendation of selected pieces of window or picture frame glass as an optical flat for this purpose makes good the claim for 'economy of means'. The various topographical features observed with this technique have been conveniently categorized in chapter 6. Appropriate mathematical expressions are given for each feature to permit measurement of the pertinent dimension. I would like to mention at this point the material included in the Appendix. This discussion of a very useful technique suffers in my opinion from the absence of drawings to illustrate the somewhat more sophisticated instrumentation employed. Furthermore, it is most unfortunate that this information was not included in chapter 6 with other methods for determining whether a feature on a sample is a depression or elevation. Figure 8. 5 should be rotated 90 ° to bring it into a~cr~ement with the text. The application of this technique to the study of metallurgical samples occupies the remainder of the book. These examples not only serve to demonstrate the extreme sensitivity of the measurement, but also hint at the range of problems amenable to the method. Even to the casual reader, these chapters provide interesting reading. The few negative comments should not dissuade those interested in the fine surface structure of metallic surfaces from acquiring this book. It is safe to say that a seasoned experimentalist using this text can soon acquire a marked proficiency with this technique.