GB700982A - Improvements relating to the production of stereoscopic images - Google Patents

Abstract

700,982. Television. ELECTRIC & MUSICAL INDUSTRIES, Ltd. Aug. 2, 1951 '[Aug. 2, 1950], No. 19257/50. Class 40 (3) Apparatus for producing stereoscopic images comprises a television pick-up tube 1 mounted on a mobile craft, such as an aeroplane and controlled so as to generate picture signals in successive frames, a pair of cathode-ray tubes 23, 24 and gated means 21, 22 for feeding the picture signals to the tubes in such manner that picture signals generated during a first sequence of frames are fed exclusively to one tube and picture signals generated during a second sequence of frames intermediate the first sequence are fed exclusively to the other tube. The arrangement is such that the images reproduced by the tubes produce a stereoscopic effect by virtue of the movement of the pick-up tube between frames. The gates may be switched at frame rate so as to exhibit alternate frames. Alternatively the switching may be effected at a sub-multiple of the frame rate so as to increase the stereoscopic base, one gate being opened, for example, during fields 1, 5, 9 &c. and the other gate being opened during fields 3, 7, 11 &c. The cathode-ray tubes may be photographed, or the images may be projected on to a single screen for direct observation, polarized light filters and spectacles being employed to distinguish the images. As illustrated the cathode-ray tubes are located remotely of the mobile craft and the signals are communicated over a radio link which may include intermediate stations. In an alternative arrangement, Fig. 1 (not shown), the cathode-ray tubes are carried on the mobile craft. In the arrangement illustrated, the switching between the two cathode-ray tubes is controlled from the transmitter on the mobile craft so as to prevent the images becoming transposed by a synchronizing signal generator 14 producing frame synchronizing signals as shown in Fig. 4 in which the number of pulses 17 and 18 differ in alternate frames. At the receiver, the synchronizing signals control the scanning in the normal manner and are also applied to a discriminator 25 which consists of a trigger circuit having one stable and one unstable state. The recovery time of the circuit when changed to the unstable state is arranged to exceed the duration of the shorter frame signal but to be less than the longer frame signal. Thus on the occurrence of odd-numbered frames single output pulses 26, Fig. 5, are produced and on the occurrence of even-numbered frames double pulses 27, 28. These pulses are then applied to an electronic relay 29 controlling gates 21, 22 so as to effect the switching of signals between the cathode-ray tubes. The stereoscopic base may be increased by employing a dividing circuit to reduce the switching rate. Cathode-ray storage tubes may be included between the gates and the cathode-ray tubes to enable images to be presented continuously.