Rubberneck Camera

A tourist who wants to see all the sights turns his head continually from side to side. So does a new, monstrous aerial camera shown last week by Perkin-Elmer Corp. of Norwalk, Conn. By twisting its optical neck as it hangs in its airplane mount, it will be capable of taking a detailed picture of the whole state of Pennsylvania in one day of sightseeing.

The camera itself does not move; mounted rigidly in the airplane, it is eight feet high, has a focal length of 48 in., weighs about 1,500 Ibs. Protruding below the plane's belly is a 90-lb. prism that rotates across the airplane's line of flight (see diagram). The prism, acting like a swinging mirror, throws into the camera lens a constantly changing view of the ground below. First the prism looks at the horizon on one side; then its glance sweeps under the airplane, then up to the horizon on the other side.

Since the image formed by the lens is a, moving one, the film must move in stept with it. In the Perkin-Elmer camera, the film is 18 inches wide and is carried in reels weighing 400 Ibs. Every time the prism makes its sweep, about ten feet of film race past the slit where the image forms. A complicated mechanism makes the film move slightly slantwise during part of its rush. This is designed to compensate for the forward motion of the airplane and keep the image from "drifting" on the film.

The result of all these tightly synchronized movements is a picture 18 in. wide and 10 ft. long, of a strip of ground extending from horizon to horizon across the airplane's line of flight. When the airplane has moved far enough forward, the prism turns again and the camera takes another picture that partially overlaps the first. The process can be kept up as long as the film holds out, covering a continuous strip of territory 100 miles wide from an altitude of 40,000 ft.

The new camera is intended for "aerial reconnaissance": quick dashes across hostile territory. It has not been flight-tested yet, but Air Force authorities believe that its pictures, taken from the substratosphere, will show such fine details as individual machine-gun emplacements and tell what sort of vehicles the enemy has on his roads.

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