System and apparatus for recording and reproducing television video signals

Abstract

The specification describes an improvement in multiple head, helical scan-type video, magnetic tape recorders. In greater detail, only one of two fields, which make each frame of the video signal, is recorded on a magnetic tape which travels at one half of the conventional running speed, the one field thus recorded is reproduced by both of the pair of magnetic heads, one after the other in succession, thereby reproducing a signal of one frame consisting of the two fields and constituting the original signal. The system and apparatus for recording and reproducing television video signals according to this invention renders it possible to record and reproduce with substantially one half of the amount of the magnetic tape compared with that required for the conventional systems.

What I claim is:  .[.1. A system for recording and playing back a video signal comprising a rotary body, means for mounting a magnetic recording and reproducing head and a magnetic reproducing head on the periphery of said rotary body, a magnetic recording medium, means for moving said recording medium past said rotary body at a predetermined speed for recording said video signal in parallel oblique tracks on said medium, means for rotating said rotary body with a velocity relative to said speed such that a video signal of one field is recorded in one track on said medium, means for applying said video signal of alternate fields to said magnetic recording and reproducing head, no video signal being applied to said magnetic reproducing head during a recording process, means for locating said reproducing head at a position on said rotary body wherein said reproducing head traces the track recorded by said recording and reproducing head with a time lag of one field period, a first means comprising said recording and reproducing head for playing back said video signal of alternate fields, a second means comprising said reproducing head for playing back said video signal of alternate fields with a time lag of one field period, and means for sequentially interlacing the signal reproduced by said first means with the signal reproduced by said second 
     
        means..]. 2. A system for recording and playing back a video signal .[.as defined in claim 1 and.]. .Iadd.comprising a rotary body; means for mounting a magnetic recording and reproducing head and a magnetic reproducing head on the periphery of said rotary body; a magnetic recording medium; means for moving said recording medium past said rotary body at a predetermined speed for recording said video signal in parallel oblique tracks on said medium; means for rotating said rotary body with a velocity relative to said speed such that a video signal of one field is recorded in one track on said medium; means for applying said video signal of alternate fields to said magnetic recording and reproducing head; means for locating said reproducing head at a position on said rotary body wherein said reproducing head traces the track recorded by said recording and reproducing head with a time lag of one field period; .Iaddend.means comprising said reproducing head for playing back said video signal of alternate fields during the recording process, said playback being for a monitoring use.Iadd.; a first means comprising said recording and reproducing head for playing back said video signal of alternate fields during the reproducing process; a second means comprising said reproducing head for playing back said video signal of alternate fields with a time lag of one field period during the reproducing process; and means for sequentially interlacing the signal reproduced by said first means with the signal reproduced by said second means.Iaddend..  .[.3. A system for recording and playing back a video signal as defined in claim 1 wherein said reproducing head is mounted at a position on the peripheral edge of said rotary body in a plane which is parallel to the plane in which the recording and reproducing head is mounted..]. .[.4. A system for recording and playing back a video signal as defined in claim 1 in which said reproducing head is mounted in a rotating plane and at a position on the peripheral edge of said rotary body which is a predetermined distance apart from the position of a rotating plane in which said recording and reproducing head is mounted, said reproducing head being another distance apart from a position diametrically opposite to said recording and reproducing head so that there is a minimum overlap of the video signal reproduced by said recording and reproducing head and the video signal 
     
     
        reproduced by said reproducing head..]. 5. A system for recording and playing back a video signal .[.as defined in claim 1 wherein said first means includes.]. .Iadd.comprising a rotary body; means for mounting a magnetic recording and reproducing head and a magnetic reproducing head on the periphery of said rotary body; a magnetic recording medium; means for moving said recording medium past said rotary body at a predetermined speed for recording said video signal in parallel oblique tracks on said medium; means for rotating said rotary body with a velocity relative to said speed such that a video signal of one field is recorded in one track on said medium; means for applying said video signal of alternate fields to said magnetic recording and reproducing head, no video signal being applied to said magnetic reproducing head during a recording process; means for locating said reproducing head at a position on said rotary body wherein said reproducing head traces the track recorded by said recording and reproducing head with a time lag of one field period; a first means comprising .Iaddend.said recording and reproducing head for playing back the video signal of alternate fields having vertical synchronizing signals in front and in rear thereof .[.and said.]..Iadd.; a .Iaddend.second means .[.comprises.]. .Iadd.comprising .Iaddend.said reproducing head for reproducing .Iadd.with a time lag of one field period .Iaddend.said video signal of alternate fields in which said vertical synchronizing signals are removed.Iadd.; and means for sequentially interlacing the signal reproduced by said first means with the signal reproduced by said second 
     
     
        means.Iaddend.. 6. An apparatus for recording and reproducing television video signals comprising a rotary body provided on opposite sides of its periphery with a magnetic recording and reproducing head and a magnetic reproducing head, a magnetic medium, means for moving said medium past said rotary body at a predetermined speed, means comprising at least one of said heads for recording said video signal in parallel oblique tracks on said magnetic medium, means for rotating said rotary body with a velocity in which a video signal of one field is recorded in one track on said magnetic medium, means for applying said video signal of alternate fields to said magnetic recording and reproducing head, no video signal being applied to said magnetic reproducing head during a recording term, means for mounting said reproducing head at a position on the peripheral edge of said rotary body which is a distance D away from the diameter in a rotating plane of said recording and reproducing head and at a position which is a distance H apart in a vertical direction from said rotating plane, a first means for reproducing said video signal of alternate fields by said recording and reproducing head, a second means for reproducing said video signal of alternate fields with a time lag of one field period by said reproducing head during reproducing time, and means for sequentially interlacing the signal reproduced by said first means with the signal reproduced by said second means, wherein ##EQU4## V indicates a magnetic tape speed, X numbers of the frame of a video signal per every second, θ angle of the recorded track on said magnetic medium to the edge of said magnetic medium, and L length of the track corresponding to a horizontal scanning period.