590 



HANDBOOK OF PHOTOGRAPHY 



Ives' System. — Figure 9a represents a scene in space photographed by a battery of 

 cameras. Figure 96 represents the scene replaced by a screen which has the charac- 

 teristic of reflecting all incident light in a horizontal plane directly back upon itself 



r" 



Scene 

 in space 



n 



Unio//recfiona/ screen 







Cameras 



O^ 



. cameras ^^ <J r^ r. 



Fig. 



(a) (b) 



9. — Diagram illustrating the steoescopic system devised by H. E. Ives of the Bell. 

 Telephone Laboratories. 



while diffusing it vertically. The cameras are replaced by projectors projecting the 



respective pictures. 



It will be seen that the eye located anywhere in view of the screen sees a vertical 



strip of the projected view from each camera. The eye, being below the direct rays 



from the projector, does not interfere. It 

 thus builds up from the various strips the 

 complete image of the original scene as it 

 appeared from its location. Since each eye 

 does this for itself, the two images are different 

 and mutually exclusive. Consequently a 

 stereoscopic image results. 



A screen having the necessary characteris- 

 tics can be made from vertical transparent rods 

 ground cylindrically on the front and rear sur- 

 faces with the rear surface painted with a 

 white diffusing paint. 



This is the method of H. E. Ives. 

 Such a system would be perfect if the 

 number of cameras approached infinity and 

 the width of the screen rods approached zero. 

 As the number of cameras decrease and the 

 width of the rods increases, the resultant 

 image becomes more obviously a series of 

 vertical strips. 



The system has been demonstrated 

 experimentally. Obviously it is enormously 



expensive and commercially entirely impractical. It is of interest as being the only 



projection system which can be viewed by a number of persons without any device at 



the eves. 



Fk;. 10. — Stereoscope viewing device 

 designed for educational purposes. 



