POLARIZING MICROSCOPE 



The writer has also been able to familiarize 

 himself with the "negative" phase-contrast 

 objectives of different makes. The image ef- 

 fects obtainable with them are of course 

 somewhat similar to those obtained by the 

 author's second method, but the pictures 

 give rather a cold impression because of their 

 grayish-white color accompanied by a metal- 

 lic sheen and a strange fogginess. As the 

 phase annuli are made by vacuum evap- 

 orization and especially as metals are used, 

 the light-absorbing layers tend to intro- 

 duce reflecting surfaces into the system. 

 Since the degree of absorption of the phase 

 annuli must be considerable in order to ob- 

 tain a very high degree of contrast, it is no 

 wonder the stray light from these reflections 

 becomes nearly equal in brightness to the 

 image itself. The soot surface, on the con- 

 trary, reflects very little. For the commercial 

 production of the new objectives, the coating 

 of soot, as it is not very resistant, must be 

 replaced by other suitable substances which 



produce the same effect. Messrs. Optische 

 Werke C. Reichert A. G., Vienna, Austria, 

 have solved this problem by using means 

 available only to a large firm of microscope 

 makers. They are now manufacturing these 

 objectives and their accessories on a com- 

 mercial basis under the name of "Anoptral 

 Contrast Equipment" (anoptral = nonre- 

 flecting). 



A. WiLSKA 



FIBERS. See GENERAL MICROSCOPY, p. 343. 



INDUSTRIAL RESEARCH, APPLICATIONS TO. 

 See GENERAL MICROSCOPY, p. 363. 



PLASTICS. See GENERAL MICROSCOPY, p. 

 390. 



PULP AND PAPER. See GENERAL MICROS- 

 COPY, p. 394. 



THEORY AND MICROSCOPE CONSTRUCTION. 

 See OPTICAL THEORY OF LIGHT MICRO- 

 SCOPE, p. 445. 



Polarizing microscope (See aUo chemical micros- 

 copy, pp. 21, 31, 52; INDUSTRIAL HYGIENE MICROSCOPY, 

 p. 400; OPTICAL MINERALOGY, p. 470) 



BASIC DESIGN AND OPERATION. See OPTI- 

 CAL THEORY OF LIGHT MICROSCOPE, p. 

 453. 



DESIGN FOR MAXIMUM SENSITIVITY 



General Description 



The polarizing microscope is a compound 

 light microscope used for studying the aniso- 

 tropic properties of objects and for render- 

 ing objects visible according to their optical 

 anisotropy. To this end a polarizing micro- 

 scope is generally equipped with a polarizer 

 and an analyzer (or "polars" following the 

 terminology of Swann and Mitchison, 30), 

 strain-free condenser and objective lenses, 



compensators, a Bertrand lens or a telescopic 

 eye piece, and a graduated revolving stage. 

 Both transmitted light and vertical illumina- 

 tion are used and the image may be studied 

 orthoscopically as in ordinary microscopy or 

 conoscopically by viewing the interference 

 pattern at the back aperture of the objec- 

 tive. Depending on its application a polariz- 

 ing microscope may also be called a pet- 

 rographic microscope, a metallographic 

 microscope, a chemical microscope, etc. 

 Many types of interference microscopes are 

 also essentially modified polarizing micro- 

 scopes. The general principles and applica- 

 tion of regular polarizing microscopes can be 

 found in several texts (1, 2, 4 to 7, 17, 22 to 



480 



