POWERFUL SEARCHLIGHT

Poverty Bay Herald, Volume LX, Issue 18236, 3 November 1933, Page 5

POWERFUL SEARCHLIGHT

ITS VALUE FOR DEFENCE 300 PARALLEL BEAMS LONDON, Sept. 10. The parallel beam searchlight, which embodies a principle now utilised for the first time, is the subject of negotiations with the Government. Manufacturing rights have been acquired by one of the biggest engineering firms. The use of this searchlight for various purposes has been discussed, but the discussions obscured its immense importance ; ini air defence and to the Navy. It is the most powerful searchlight in th© world—no less than 3,000,000,000 candle power—and it has been reported upbii by Air Ministry and War Office experts in emphatically favorable terms. It is as great' an advance over existing searchlights as was “steam" over “sail” in shipping. It secures intensity of illumination at a great range. Its Secret is the combination of a large reflector of parabolic form, and a mosaic’ of 300 small, fiat mirrors on a fiat disc. The illuminating agent is placed be-, tween, and the mirrors convert the familiar cone-shaped beam into 300 parallel beams. A cone-shaped beam could quite easily be projected by this apparatus, but even in this case the waste of light would be negligible. The loss of light, in fact, is only the unavoidable 5 per cent, in the reflector, and a further per cent, due to the minute divisions between the mirrors. For many years famous optical firms in France and Germany tried to solve this problem, which was at length overcome by a British inventor. The beam is so powerful that a newspaper five miles from the searchlight 'can be read in it. As an anti-aircraft searchlight its value lies in the fact that any pattern can be projected into the sky. Of course, ah ordinary searchlight can send a pattern by means of an interposed' screen, but only with very great loss of light. By means of the parallel beam searchlight a “grid” pattern can be sept, a chessboard pattern of squares, the dimensions of which being known reveal .the' height, speed, and direction on an caught in the beam. This has been raised to a height of 36,00Qft.