GB1285745A - Magnetic recording system - Google Patents

Abstract

1285745 Television INTERNATIONAL BUSINESS MACHINES CORP 11 Dec 1969 [14 Jan 1969] 60453/69 Heading H4F In a video signal recording system a magnetic tape is moved past a multi-gap recording head and each gap is sequentially energized with a signal proportioned to the intensity of an elemental area of a line scan of the image to be recorded. In Fig. 1 a pattern of magnetization representing image 11 is recorded on tape 10 by scanning the image from bottom to top successively along paths A, B and C, the resulting signals being recorded in rows of bit cells along tape 10, one cell from each row being associated with each scan A, B, C &c. The mode of recording is such that when a black area is scanned an area 19 of the cell 16 is magnetized in one direction whilst the remainder 20 of the cell is magnetized in the opposite direction, area 19 being large compared with area 20. The opposite is so when a white area is scanned e.g. area 21 is small compared with area 22. Although only three tracks on the tape are shown for each of the areas 12, 13 and 14 of the image, a total of about 500 tracks is usually employed. In Fig. 2 the windings 41 of the recording head are sequentially energized by the output from an image electronic scanner e.g. an orthicon, vidicon or image disector, each line scan of which is initiated by a pulse from timing control 32. A train of pulses is simultaneously fed from control 32 to counter 35, the outputs of which sequentially gate sample and hold (SH) circuits 37, 42 &c. The output of each SH circuit, which represents the amplitude of the signal on line 31 is applied to the junction of a resistor and capacitor and to the input of a flip-flop circuit which energizes the associated recording winding 41 for a period proportional to the amplitude of the signal from the SH circuit. The finaltwo stages 46 of counter 35 are not utilized since they accommodate the fly-back time for each scan of scanner 30. In a second embodiment (Fig. 4, not shown) the tape may be held stationary while each transverse scan is recorded, and the SH and flip-flop circuits may be replaced by an amplifier which develops a current analogue representing the scanner output, and a switching circuit. The tape prior to recording is preferably magnetized in the opposite direction from the recorded areas. Playback may be effected using a magnetooptic readout the tape being moved intermittently (Fig. 6, not shown) the resulting optical image being directly viewed or televised. For colour recording, the three colour pictures may be recorded as separate images, their magneto-optic images being optically superimposed using either colour sources or filters.