MECHANICAL EYES OF WAR

New Zealand Listener, Volume 3, Issue 55, 12 July 1940, Page 4

MECHANICAL EYES OF WAR

Televising Troops From The Air

| NE of the mechanical wonders of O this war is the gun-plotting camera, which is in use on practically every British warship. This ingenious machine, one of the many new mechanical eyes of war, looks like a tiny anti-aircraft gun. It is armoured and moves on a turret-head rather like a motion picture camera. The gunplotting camera is used for low angle marking; it records with the greatest accuracy how far a shell falls outside the range of its intended target. Within a few minutes the negatives can be developed and printed and the error corrected during the course of an engagement, Mechanical eyes of war have improved vastly since 1918 and are responsible for the extraordinary accuracy of the British naval and anti-aircraft guns. But for these new devices it would be almost impossible to fight a war with long-range guns, bombers which fly in the stratosphere, and anti-magnetic minesweepers. During a sea battle, if by chance you were on a British warship, you would see a naval rating quickly handling a gunplotting camera, one of the most important of the new devices. Such cameras are in constant practice and speed up the once laborious job of gun-plotting, which included calculating the range of the enemy ship or ’plane, the trajectory of the shell, and the charge. Now it is all done in seconds and in addition to the time gained saves a great deal of money, if you remember that each 16in. shell from a naval gun costs over £1,000. When such shells fail to hit their targets war expenses soar. Range of Error The new British 4.5in. anti-aircraft guns would be practically useless without their predictor mechanism, which includes long-distance range-finders. Until the introduction recently of these new "mechanical eyes" it was necessary to have a range-finder nearly 100 feet long to reduce possible technical error to 100 yards at 20 miles; or a range-finder 10 feet long to reduce the error to 100 yards at 10 miles, and so on, These range-finders are intricate technical instruments, requiring the services of men who have been long trained in their use. Briefly they may be explained as follows: Two prisms, with their accompanying optical groups are used; one introduces a 90 degree beam to the observer, the other shows an image at the eye-piece in a position which depends, of course, on the distance. This instrument is similar to the "moving image" or double image range-

finders in use on many cameras. When the operator looks through the eyepiece he sees two pictures of his target. Those two pictures are brought together by moving the control. When the two images have merged into one the correct range has been found and the distance shows on a meter. The latest military versions of these range-finders are speedy and accurate to an astonishing degree. Another device recently invented enables range-takings to be photographed on a sensitised film-strip. These findings are afterwards checked with negatives taken in the low-angle marking cameras. The lenses and prisms used in the new range-finders must be as near perfect as possible because of the super-accuracy demanded of them. They must be so accurately ground that ordinary commercial methods’ are useless. Even the vibration of passing traffic, which was not felt by the workers themselves in one military factory, was sufficient to spoil the delicacy of the. polishing required. Here was a new difficulty, but it was overcome. A special factory wing was built on a base of 8 feet of concrete. The steel machine beds were slung on damped spring and rubber bufferseach cradle holding five tons of the grinding and polishing machinery, The only connection with the earth itself was the electric cable which conveyed power to the 4 horse-power grinding motors; and the skilled workmen sat in slung saddles. Those workmen are among the most highly skilled in their trade and they spend from six to seven hours a day sitting on springs and sponge rubber. Many of the Royal Air Force flights which have been made over enemy territory are for the purpose of taking stereoscopic pictures of the country below them. This is done with dual automatic cameras and the work resembles the process of contour sketching, except that it is done with a camera. At the moment optical experts are working with the manufacturers of gyro-con-trolled pilots, or automatic pilots, with the object of producing stabilised chassis for this new form of aerial photography. Submarine Periscopes The periscopes of submarines, although not vastly different from the pattern of 1914-18 types, have been improved. British underwater craft of this war have now been fitted with a special type which gives a minimum wake when it cuts through the water, thus reducing the possibility of being recognised from the air or from enemy ships. Magnification, field view and clarity of vision are much better than they were even ten years ago, and the optical experts are still working to improve them. It is also possible to "televise" troop movements to-day. This mechanism consists of a pair of telescopes, one the

right way round, the other inverted. The new British periscope incorporates a range-taker which, at the touch of a control, enables a "close-up" to be recorded. Italian engineers have developed an ingenious mechanism which enables the movements of troops on the country below them to be televised by means of a television scanner, By this means a reconnaissance pilot is able to transmit to his base a moving picture of enemy territory. The received image can be photographed on a 35 millimeter film strip as a permanent record, in addition to giving an instantaneous picture of moving troops to the gunnery experts at headquarters,