SUBSTAGE CONDENSERS AND CONDENSER MOUNTS 117 



condenser mount. The diaphragms possess a cross-shaped aperture 

 and are mounted in a plate which is centerable after it has been fitted 

 into the substage mount. I. Koristka and Co. also makes a single-unit 

 condenser mount for its "simplified" phase microscope stand. 



A design which has been very convenient includes a rotatable plate or 

 turret mounted at or near the first focal plane of the substage condenser. 

 As a rule, the rotatable plate carries four diaphragms and has at least 

 one clear aperture. Any one of the diaphragms or the clear aperture can 

 be rotated into position for use below the substage condenser. The 

 combination of a rotatable turret and either a multiple, revolving nose- 

 piece or a quick-change nosepiece permits rapid and convenient changes 

 from one phase objective to another or from phase microscopy to 

 ordinary microscopy. The clear aperture is also helpful during the 

 procedure of aligning the phase microscope. Figure 111.5.1c and 

 Figs. III. 5. 2a and III. 5. 25 are illustrations of the general appearance of 

 substage condenser mounts with a rotatable changer plate. 



Most of the manufacturers offer a substage unit with a revolvable 

 plate. The greatest point of difference between such substage condenser 

 mounts lies in the centering action provided for the condenser dia- 

 phragms. Some manufacturers such as Wild Co. and the American 

 Optical Co. have made each diaphragm in the changer individually 

 centerable. If each of the diaphragms in the changer is initially 

 centered with respect to its corresponding phase objective, then these 

 phase objectives together with their corresponding diaphragms may be 

 interchanged without the necessity of interrupting the observation in 

 order to recenter a condenser diaphragm. For rapidity of procedure 

 together with best performance, either the objectives should be centered 

 to a common optical axis by the maker, or the objectives should be 

 mounted in quick-change, centering nosepieces. 



Figure 111.5.1c shows the turret substage unit supplied by the 

 American Optical Co. (1949). The wrenches are inserted into the upper 

 guides to center the condenser diaphragms. Figure III. 5. Id is a bottom 

 view of a similar substage turret mount modified slightly to fit a later 

 model of microscope stand. The condenser is of the Abbe type, 

 N.A. 1.25, and is separately centerable. Figures III. 5. 2a and III. 5. 26 

 show, respectively, a top and bottom view of the condenser mount 

 with a revolving changer plate for diaphragms as supplied by the Wild 

 Co., Ltd. (1949). Figure III. 5. 2c is a photograph of the Wild stand 

 listed as a research and routine microscope for medical purposes and 

 fitted with the substage condenser mount shown in Fig. III. 5. 2a. 

 Centering wrenches and the auxiliary centering telescope are also 



