in focus or change in distortion. Final computed data is not yet available, 
since the lens is still in the development stage, but tests made in the 
Fairchild Camera Calibration Laboratory on the prototype show the average 
distortion value to be 3 microns. The illumination characteristics are such 
that the light energy over the field is homogeneous when a cos^ vignetting 
coat is applied to the filter. 
The 14 element lens and the filter are housed in meehanite cells, this 
material having been selected for its closely matching coefficient of expansion 
to glass and for its excellent stability. A mapping lens, it has the tremendous 
advantage of a central air space of 0. 350 inches. This permits the use of 
the drawer-type between-the-lens shutter similar to that developed for the 
T/ll and KC- 1 cameras, which can be removed“, if necessary, for maintenance 
or repair purposes without disturbing the inner cone assembly, and thereby 
voiding the calibration of the camera. This is shown in Figure 3. 
Computer procedures will be employed during manufacturing stages to control 
the measured optical characteristics and thereby optimize them within the limits 
of the design. Both laboratory and aerial tests are scheduled which will fully 
evaluate the performance of this latest wide angle American mapping lens. 
Magazine Platen and Reseau 
The platen comprises a casting of stabilized beryllium heavily ribbed to maintain 
the flatness of its surface under operation and over the range of earthly environ 
ments, the total deviation from a plane not exceeding 0. 00010". During opera 
tion of the magazine, the vacuum holds film in firm contact with the surface 
of the platen while the platen, in turn, is supported on the moving guide surfaces 
of the inner cone. During the exposure cycle the platen moves in a plane 
accurately parallel to the focal plane, accurately locating the emulsion side 
of the film against the focal blocks. Spring loading of the platen against the 
blocks maintains location during translation. 
The problem of dimensional instability of film is controlled by the use of a 
5x5 pattern of illuminated dots, approximately 35 microns in diameter, 
forming a reseau on the film (see Figure 4). The nominal pitch between any 
two adjacent coordinated dots is 50 millimeters. These dots are generated 
through miniature optical projection systems consisting of a pinhole reticle, 
a projection lens, and a flash system imbedded and sealed in the platen. The 
reseau is flashed on the emulsion through the base of the film at the instant 
the shutter is opened to expose the format and, since the film is stationary 
with respect to the platen during exposure, dot size and shape are not affected 
by IMC motion. During manufacture, reseau dots are positioned to nominal 
tolerances. Their accuracy is determined during camera calibration with a