Patent GB-1162637-A (GB)
Title: Colour Video Signal Recording and Reproducing System
IPC: H04N1/64
Filed: 1967-01-31
Abstract: 1,162,637. Magnetic recording and reproducing of colour video signals. SONY CORP. 31 Jan., 1967 [31 Jan., 1966 (2)], No. 4682/67. Heading G5R. [Also in Division H4] A colour video signal recording and reproducing system comprises: an image pick-up tube, a rotary colour filter having section - ized colour filters, driving means for the rotary colour filter, means for generating index signals corresponding to the rotation of the rotary colour filter, gate circuits for deriving different colour signals obtained from the image pick-up tube, gate-signal-generating means for controlling the gate circuits, these means being controlled by the index signals, a start switch for operating the gate circuits, a rotary magnetic sheet, driving means for the magnetic sheet, magnetic recording heads, means for recording the different colour signals respectively on the sheet with the recording heads, such recording being controlled by the start switch, and means for reproducing the different colour signals recorded on the sheet. Signal sequencing and recording.-A rotary colour filter 7, angularly divided into red, green and blue regions, is driven by a device 6 to rotate once in 10 seconds between a colour still picture (not shown) and a monochrome vidicon pick-up tube 2 in a camera 1. A cam fixed to the shaft of filter 7 is arranged to operate contacts 8R, 8G, 8B immediately before the red, green and blue filter regions respectively move in or out of relationship with the pick-up tube 2. The signal from camera 1 is fed through a composite circuit 9 and a frequency modulator 10 to three gate circuits in parallel, 11R, 11G, 11B for red, blue and green signals respectively. The duration and sequencing of the signals actually passed through the gates are determined by a gate signal generator 12 associated with the contacts 8R, 8G, 8B. When a recording push-button switch 16 incorporated in the gate signal generator is pressed, the gate circuits 11R, 11G, 11B successively each pass on video signals representing one or more frames only of the incoming video signals through respective amplifiers 18R, 18G, 18B and recording contacts R of switches 19R, 19B, 19G to magnetic recording heads HR, HG, HB. The heads are in contact with a rotating magnetic recording sheet 21 but are spaced apart radially at predetermined intervals, and are moved inwards simultaneously by a positioning device 22 to produce spaced tracks TR, TG, TB during recording. The sheet 21 is rotated at 30 revs/second by a synchronous motor. The recording of each picture is selected to be of 40 to 50 seconds' duration. Synchronizing.-The rotary shaft 23 of the magnetic sheet 21 has secured to it a pair of pulse generators 24, 25, angularly spaced 180 degrees, which produce synchronizing pulses of frequency 30 Hz phased 180 degrees apart. Another pulse generator 26 produces horizontal synchronizing pulses of frequency 15.75 KHz. All these signals are applied to a synchronizing signal processor 27, from which are derived pulses PF of frequency 30 Hz, vertical synchronizing pulses PVD of frequency 60 Hz (which are fed to camera 1 at 4V) and horizontal synchronizing pulses of frequency 15.75 KHz (which are fed to camera 1 at 4H). Pulses PF, and also pulses PF<SP>1</SP> derived therefrom by a delay circuit 17, are both used in the gate signal generator 12. The camera 1 produces the video signal at 3 and the synchronous signals at 5, and these are combined in the composite circuit 9 so that the synchronizing signals are recorded with the video signal. Playback.-For this purpose the magnetic heads are connected through contacts P of switches 19R, 19G, 19B through amplifiers 28R, 28G, 28B, and through demodulators 29R, 29G, 29B to a colour picture tube 30, and the tracks TR, TG, TB areplayed back repeatedly to produce a still colour picture in a manner analogous to a colour slide projector. Re-recording.-For this purpose a servo circuit 40, including a comparing circuit, is provided for synchronizing rotation of the magnetic sheet of the re-recording apparatus (not shown) with rotation of the magnetic sheet 21 of the main recording apparatus. (The re-recording apparatus has some, only, of the features of the main apparatus, and other features: the common features are identical). The servo circuit 40 is fed with pulses PF, as shown, and with pulses equivalent to PF from the re-recording apparatus at an input terminal 43. The resulting error signals are used to control a magnetic brake 42 fixed to the rotary shaft 23. With switches 19R, 19G, 19B in playback position, the output sides of the amplifiers 28R, 28G, 28B are connected through switching circuits 44R, 44G, 44B to output terminals 45R, 45G, 45B; these latter are connected, through a set of amplifiers in the re-recording apparatus, to recording amplifiers, recording switches and recording heads exactly equivalent to parts 18R, 18G, 18B; 19R, 19G, 19B and HR, HG, HB. The switching circuits 44R, 44G, 44B are controlled by a re-recording switch 46, multi-vibrator circuits 47, 48 and a delay circuit 49. The vidicon tube 2, having a relatively long residual image time constant, avoids colour mixing and ensures provision of a vivid colour picture. In a modification (Fig. 3, not shown), an image orthicon tube is used, in which case contacts 8R, 8G, 8B are replaced by a single contact, and in the gate signal generator there are minor modifications, including replacement of circuits 13R, 13G, 13B by others; the driving device 6 is controlled by the vertical synchronizing pulses. The colour filter in this case rotates at 20 revs/second.