CH. VII] PROJECTION OF IMAGES OF OPAQUE OBJECTS 193 



The projection objective is of the Tessar Ic series of very large aperture 

 (114 mm., 4T3 in., in diameter and 50 cm. 19^ in. equivalent focus). The 

 focusing is accomplished by a screw which raises or lowers the table supporting 

 the object. 



This instrument enables one to demonstrate to an audience the workings of 

 a machine like a cash register, or a quarto size page of illustrations or print. 

 With the vertical objective and a mirror to reflect the light to the screen the 

 image will be erect. The reflecting mirror is silvered on the front to avoid 

 the doubling of the image. 



FIG. 108. MODEL 5 DELINEASCOPE FOR OPAQUE AND LANTERN-SLIDE 



PROJECTION. 

 (Cut loaned by the Spencer Lens Co.), 



With the arc lamp and the first element of the condenser in a horizortal 

 position the light extends directly to the right through the lantern slide or 

 other object and the projection objective, or projection microscope, or it ir.ay 

 be reflected upward through the vertical projection microscope (fig. 175). 



For opaque projection, the arc lamp and first element of the condenser are, 

 by means of the crank, rotated within the lamp-house to the right position to 

 direct the light upon an opaque object in a vertical or in a horizontal position 

 as desired. 



If the object is in a horizontal position the light from it is reflected to a mirror 

 and from the mirror out through the large projection objective. It will appear 

 correct in the screen image. The vertical object will have the rights and lefts 

 inverted. Objects or surfaces 15x23 cm. (6x9 in.) can be projected with 

 this instrument. 



