GB1168854A - A Method of Echo Ranging and Recording and an Apparatus for Performing such a Method - Google Patents

Abstract

1,168,854. Echo ranging. J. D. RICHARD. 8 May, 1967, No. 21374/67. Heading H4D. In an echo-ranging system the echo signals intensity modulate the beam of a cathode-ray tube (C.R.T.) whose faceplate incorporates a luminescent phosphor and a fibre optics matrix, and a photo-sensitive paper strip is moved across the faceplate to provide a graphic record of the echoes. In the Fig. 7 embodiment for marine use, the repetition frequency of pulse generator 96 is set proportional to the local speed of sound in water and frequency dividers 97, 98 provide range marker pulses corresponding to 100-fathom intervals (4 p.p.s.) and 10-fathom intervals (40 p.p.s.). Bi-stable circuits 82, 84 control gate 81 to pass two of the 4 p.p.s. pulses to open gate 72 and so cause a pair of acoustic pulses to be transmitted. The sea-bed echo of the first acoustic pulse triggers monostable 78 which opens gate 79 for a time sufficient to pass two of the 4 p.p.s. pulses to C.R.T. sweep trigger 88, so that the C.R.T. saw-tooth sweep is started by the first of the 4 p.p.s. pulses and stopped by the second, i.e. the sweep interval corresponds to 100 fathoms. In this interval the 10-fathom marker pulses and the echoes of the second acoustic pulse intensity modulate the C.R.T. beam to illuminate phosphor 93. The photo-sensitive paper strip is drawn past fibre optics matrix 92 set in C.R.T. faceplate 91 and the recorded image may be heat-developed. A gate 87, opened by the first transmitted acoustic pulse and closed by its sea-bed echo, passes the 4 p.p.s. pulses to a counter/printer 90, so that the depth of the sea-bed and fish shoals above are indicated by the counter reading (in hundreds of fathoms) plus the " vernier " distance along the displayed C.R.T. time-base. The speed of movement of the paper over faceplate 91 may be made proportional to the speed of a ship carrying the echo-ranging apparatus and may control the repetition period of the echoranging cycle. The recorded echoes can be displayed by positioning a luminescent panel behind the (translucent) paper strip (Fig. 5, not shown). In a modification the C.R.T. sweep is initiated by the sea-bed echo of the first transmitted acoustic pulse and stopped by the sea-bed echo of the second. In a second embodiment (Fig. 1, not shown) a single acoustic pulse, rather than a pair, is transmitted in each echo-ranging cycle and the C.R.T. sweep is started by the transmission (with or without a delay) and lasts a predetermined time. For echo-ranging in the atmosphere or space, electromagnetic energy is transmitted instead of acoustic energy. In an embodiment (not shown) for recording the depth of reflecting objects (e.g. fish) within the sea from an aircraft the energy source is a laser generating pulses in the green portion of the spectrum and the C.R.T. sweep is triggered by the energy reflected from the sea surface to give a recording referenced to the sea surface.