CH. IX] 



HIGH POWER MICRO-PROJECTION 



279 



FIG. 155. 



THE EFFECT OF USING AN IRIS DIAPHRAGM IN THE CONE OF 

 LIGHT FROM THE MAIN CONDENSER. 



The second element of the condenser is shown at the top. The focus of 4 the 

 cone of light from the condenser is shown at F, the axis by A . 



B At the right are shown in millimeters, three diameters of the cone of light 

 with three different openings of the iris diaphragm (22, 33, 44 mm.) 



C At the left are shown the apertures corresponding with these openings 

 in the iris diaphragm (23, 34, 45). The aperture of these openings is also 

 shown above the circles. 



One can see by this diagram what an enormous amount of light is lost by 

 making the illuminating cone smaller. 



