GB252387A - Improvements in or relating to scanning devices for television systems - Google Patents

Abstract

252,387. Metropolitan-Vickers Electrical Co., Ltd., (Assigness of Whitten, W. H.). May 25, 1925, [Convention date]. Television apparatus. -The exploring movement of a mirror in a television system is effected by the expansion and contraction of a piezo-electric crystal. Two crystals may be employed, one expanding when the other contracts. The figure shows a transmitting arrangement. The crystals 4, 5 are each mounted at one end on a base 6 on the wall of a receptacle 8, and their other ends bear against the back of a mirror, comprising a deposit 3 of silver on a glass support 2, one at each side of a controlling spring 9. Metal plates 10, 11 and 12, 13 arranged on either side of the crystals 4, 5 respectively are connected as shown to an a-c generator 15 producing e.g. 1000 cycles per sec. A fixed mirror comprising a surface 18 of silver on a glass support 16 is mounted in the receptacle 8 behind the oscillating mirror 3, and the receptacle is filled with a mixture of alcohol and glycerine having a refractive index equal to that of the glass supports 2, 16. The image 22 to be transmitted is focussed by a lens 21 on to the mirror 18 and the beam, after repeated reflection as shown from the two mirrors, is incident on a third mirror 24 mounted on an armature 27 oscillated about an axis 29 at right angles to the axis of the mirror 3 by a polarized electromagnet 26 to which current is supplied from an a-c generator 31 at e.g. 16 cycles per sec. The beam reflected from the miror 24 traverses a photoelectric cell 30 and light from successive elements of the image is thus incident on the cell. The image is reproduced at the receiving station by mirrors oscillating synchronously with the mirrors 3 and 24.