REFRACTION OF LIGHT, REFRACTOMETRY AND INTERFEROMETRY 



the content of these articles with the pubHca- refractometry was extended to the infrared 



tion date. by Rodney and Djurle (178). 



Refinements to the prismatic refractom- Direct refraction measurements on the 



eter continue to appear. Svenson (161) ex- atmosphere have now been extended to the 



tensively studied several forms of this re- radio-waves domain. Basic computations 



fractometer. This type of instrument lends were given by Johnson (179). Straight re- 



itself to automatic direct reading (Johnsen fractometric methods (Grain: 180, Grain 



and Schnelle: 162) as well as to self-balancing and Deam: 181), phase-shift techniques 



techniques (Penther and Noller: 163). (Tolbert and Straiton: 182), diffractometry 



Gonsiderable effort is currently devoted to (Bachynski and Bekefi: 183) and interferom- 

 refractometric measurements in the infrared etry (Artman: 184) are now currently used 

 radiation domain. The dispersion of Stand- for such measurements, 

 ard dry air in this region is now extensively The introduction of Information Theory 

 tabulated, together with the depolarization in optics leading to new advances in this 

 factor of atmospheric gases and Rayleigh's field (Linfoot: 185), a better understanding 

 scattering cross-section (Penndorf: 164). of certain limitations of optical elements 

 Spectrometric methods are available in this (Jones: 244), and a mastery of wave fronts 

 domain (McAlister et al.: 165), as well as an (Zernicke: 186) and of their use in image re- 

 arsenic trisulfide glass hollow-prism instru- construction (Kirkpatrick et al.: 187), are 

 ment (Jaffe and Oppenheim: 166), and a developments which must be recorded. Some 

 modified goniometer (Traub and Osterberg: of these advances are embodied in new in- 

 167). Accurate observations made with a struments such as the Kapany fiber-glass re- 

 Capehart-Farnsworth IR image converter fractometer (188) based upon the properties 

 tube — a method proposed, but not used, by of coated dielectric cylinders (Kapany and 

 the writer in 1954 — have now been reported Pike: 189). A commercial version suitable 

 (Garlan and Paul: 168). By far the greatest for industrial control is now described in the 

 advances in the infrared region have been chemical literature. The fiber-glass refrac- 

 gained by the use of interferometric methods tometer is really making use of the critical 

 which permit both the frequency calibration angle phenomenon. The instrument of For- 

 of spectrometers (Brodersen: 169, Bolster: rest and Straat (190) for glass production 

 170) and the measurement of secondary control falls in this category. An exhaustive 

 wavelength standards (Rank et al: 171). study of errors in this type of measurements 

 The Greenler instrument (172) appears par- is due to Forrest (191). 

 ticularly well adapted to these measure- Previously clear-cut delineation between 

 ments. A simple filter device has also been ^^^ ^^l^s of microscopy, refractometry and 



1 1 T^ • J T\/r c ij /i'7o\ interferometry tend to disappear in con- 

 used by Kagarise and May field (173) ; a ^ , , t^ - , 



^■n J T^ •, -r, . , 1 1 temporary technology, ror mstance, the 



modified l^abry-Perot etalon was proposed ,, , ,. ,, r ■ , • i 



, „ , • /i«.N 1 ^-n 1 T-,, schlieren retraction technique has now 



by (Jppenheim (174) and a modified Fibert ^ j^ixxi, ^r- 



, . , . „ . been adapted to the measurement of micro- 



monochromator with interferometric modu- • ,• i ^-^t a -,, iao\ i 



scopic particles (Meyer- Arendt : 192), and 



lation has been used by Strong (175) in the ^^e Polanyi difi^ractometer (193) yields the 



far-mfrared. The Gasey-Lewis filter (176) is, number, volume and index of red blood cells 



in reality, an infrared interferometer. As a i^ suspension. The interferometric study of 



result, a dispersion formula for air in the Hying cells has been reported by Barer (194) 



near infrared more exact than that previ- while the polarization interference micro- 



ously given, was recently published by scope has been extensively investigated by 



Schlueter and Peck (177). Phase-contrast Frangon (195). Such hybrid techniques are 



520 



