124 



INSTRUMENTATION 



the condenser proper and a rotatable turret arrangement which contains 

 a large free aperture, a smaller free aperture, and one centerable con- 

 denser diaphragm with an annular aperture for phase microscopy 

 (Fig. III. 5. 8). The pancratic system forms an image of the annular 

 opening at the first focal plane of the condenser proper, and the magni- 



FiG. III. 5. 7. Zeiss-Winkel phase contrast microscope with turret changer plate 

 for diaphragms. Courtesy of R. Winkel G.M.B.H. (1949). 



fication of the pancratic system can be varied so that the size of the 

 image of the annular aperture can be changed to fit the conjugate area 

 of any of the phase objectives. Zeiss, Jena (1949) provides phase ^ 

 accessories also for the Lumipan stand with a pancratic condenser 

 system. 



In order to meet the requirements of phase microscopy with slides of 

 greater than standard thickness or with specimens contained in small 

 cells or flasks, both the Bausch and Lomb Optical Co. and the American 

 Optical Co. supply, in addition to a N.A. 1.25 condenser, special phase 

 condensers which have a long working distance. The Bausch and 

 Lomb long working distance condenser may l)e used with its series of 

 both the dry and the oil immersion achromatic objectives for phase 



