Ch. Ill] 



BINOCULAR MICROSCOPES 



8S 



While more or less successful efforts had long been made to produce 

 binocular microscopes with a single objective, the optical requirements 



Ocular 1 



2^lar 



Fig. 53. Ives Binocular Arrangement for All Powers. 

 (Journal of the Franklin Institute, Dec. 1902). 



Objective The single objective. 



pb The prism box at the lower end of the tube. 



a,b,c The prisms dividing the light equally from each point to the two eyes. 



a, b The transparent silvered surface in the prism allowing half the light to 

 pass through and half to be reflected to the right. 



c Prism at the right reflecting the light upward to the right eye, as, ad- 

 justing screw to tilt the prism c, at the correct angle for the position of the 

 right ocular. 



apd Adjustment for the pupillary distance. 



Ocular, I, Ocular 2 The oculars for the right and the left eye. • 



Axis I The principal optic axis for the left eye. 



Axis 2 The principal optic axis for the right eye. 



Due to the length of the prism c, this axis is optically of the same length as 

 Axis I for the left eye. 



were not fully grasped. Recently, however, Mr. Frederic E. Ives 

 has stated the optical principles with great clearness, and shown how 

 binocular microscopes using a single objective can be constructed. 



