REFRACTOMETRIC APPLICATIONS 



now the topic of large international s^aiiposia theory was developed by Saunders (213) are 



(Frangon: 196). multiple beam devices based upon the prop- 



The technical advances of recent years erties of crystalline films but Fabry-Perot 



have been made possible by parallel ad- etalons can also be used in the same man- 



vances in theoretical optics. For instance, a ner (Post: 214, Primak: 215). Application 



revised, more general theory of the Fabry- to the refractive index of liquids was carried 



Perot interferometer was offered by Vander out by Bakarat (216), who built a specialized 



Sluis and McNally (197), and a fruitful vec- form of the instrument for this purpose 



tor theory of the Mach-Zehnder interferom- (Bakarat and Nooh: 217). 



eter was completed by Bennett and Kahl All interferometric methods have common 



(198). Many technical refinements become problems. Variable contrast between fringes 



possible by introducing the concept of par- of different order presents difficulties (Price 



tial coherence (Thompson: 199) on a solid and Wedaa: 218). Correlating readings and 



mathematical basis (Thompson and Wolf: wavelength is another problem (Hirschberg 



200). and Kadesch: 219). Apparent fringe width 



In recent years the Jamin Interferometer variability has received special attention 

 has been modified in many ways (Lotman: (Leadon and Werner: 220-221, also Winkler: 

 201). The introduction of a total reflection 222). Various spectral effects have been con- 

 prism led to the construction of the Riken sidered by Kahl and Sleator (223), and by 

 instrument (Namba: 202) for isotope analy- Koester (224). 



sis. Similarly, corner-mirrors are used by Recording techniques are now currently 

 Peck (203) in a variant of the industrial used conjointly with such diversified inter- 

 beam-splitter interferometer. A further sim- ferometers as the Riken type (Namba : 225) , 

 plification ("common-path" interferometer) the Fabry-Perot type (Biondi: 226) and the 

 of this industrial instrument is due to Dyson beam-splitter type (Hasa and Smith : 227) . 

 (204) . The variable pressure gas compen- In the device of Peters and Stroke (228) the 

 sator is enjoying a renewed popularity (Rank exit beam is divided by a Wollaston polar- 

 and Shearer: 205), simultaneously with the izer and is modulated by a rotating polaroid, 

 development of hybrid measurement meth- Directional counting of fringes has been ob- 

 ods such as that combining interferences tained by the use of four phototubes (Eisner : 

 with the "Schlieren" method (Temple: 206). 229). An exhaustive evaluation of the re- 

 This path was also explored by Ingelstam cording problems in interferometrj^ is due to 

 (207) . The Fizeau method also has been fur- Stroke (230) . 



ther improved (Osterberg and LaMarre : Concerning the use of Rayleigh type inter- 



208). ferometers for measurements on fluids, the 



The Mach-Zehnder interferometer con- dispersion error was extensively evaluated 



tinues to be modified in many different ways by Grunwald and Berkowitz (231). They 



to suit specific purposes (Price: 209). A spe- devised an elaborate correction method 



cial construction is available for measure- which does not seem to offer many advan- 



ments on volatile liquids (Caldwell, Hall and tages over that previously mentioned. 



Babb: 210), for heat transfer study (Mc- The list of applications continues to grow. 



Lean, Scherrer, Nanney and Faneuff: 211), A combination of interferometric and spec- 



and for aerodynamic investigations (Blue trometric methods has been used by Ellis 



and Pollack: 212). (232) to study plastic films. Precision analy- 



The newer "series" or "in-line" inter- sis of D2O-H2O mixture is due to Ingelstam 



ferometers for industrial applications, whose and co-workers (233) , using a phase-contrast 



521 



