JPH0373923B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus (hereinafter referred to as a VTR) for long-term recording and monitoring, which records video signals by dropping frames using an intermittent recording method.

In general, VTRs used for surveillance in banks, parking lots, etc. record intermittently in order to enable long-term recording. Conventionally, long-term VTRs using this intermittent recording method were of the two-head type. It was hot. In such conventional devices, the conventional 1/2-inch helical scan method performs one frame intermittent recording at the standard tape speed of the magnetic tape by matching the timing of intermittent running of the magnetic tape with the timing of recording. Although the tape was compatible with VTRs, control such as increasing the tape speed to the standard tape speed during intermittent running and maintaining that speed during recording was complex and difficult. In addition, the other method uses the same azimuth recording, so it is different from the conventional method.
The tape is not compatible with the VTR, and since the same field is recorded, the horizontal synchronization signals on the tape pattern do not line up between adjacent tracks.
There were cost disadvantages such as the need for a correction circuit for this purpose.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional system, and uses a pair of video heads mounted at symmetrical positions on a rotating drum with a difference in height of one track width between them. Recording and still image playback are performed, and normal playback is performed by another pair of video heads installed at symmetrical positions on the rotating drum, thereby eliminating the need for special high precision in the magnetic tape drive system. Moreover, by providing a predetermined azimuth angle on the video head, recording is made compatible with the conventional VHS format or Beta format.
It is an object of the present invention to provide a magnetic recording/playback device that can perform playback.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figures 1a, b and 2 are diagrams showing the positional relationship between a rotating drum of a magnetic recording and reproducing apparatus according to an embodiment of the present invention and a group of video heads arranged on the rotating drum, and a recorded tape pattern. In the figure, 3 is a rotating drum, and 1 and 1' are a pair of first video heads having a predetermined azimuth angle mounted on the outer peripheral surface of the rotating drum 3 symmetrically with respect to its central axis. The step difference Tw between these video heads 1 and 1' is selected to be one track width. Reference numerals 2 and 2' denote a pair of second video head groups having a predetermined azimuth angle and are mounted perpendicularly to the first video head group 1 and 1'; 4 is a magnetic tape; 5 is a magnetic tape; In the running direction of the magnetic tape 4, h is an interval of one frame. here,
It is not necessary to select a particularly large step difference between the second video head groups 2 and 2'.

Next, the operation will be explained.

First, during recording, a recording circuit (not shown) is controlled so that the first video head group 1, 1' records only one frame during the stop period of intermittent running.
The recording patterns by the video head groups 1 and 1' are tracks a and a' shown in FIG. When the recording for one frame is completed, the magnetic tape 4 is run for one frame in the running direction 5, and the next frame is recorded.

Next, during standard playback, the magnetic tape 4 is run and played back by the second video head group 2, 2'. What is shown by the broken line and the dashed-dotted line in FIG. 2 are the trajectories of the second video head group 2, 2', respectively, and in this case, portions b and b' shown by diagonal lines in the figure are obtained as reproduced signals. During this standard playback,
As shown in the figure, the trajectories of the second video head group 2, 2' do not match the recording tracks a, a', but this is because the head widths Hw, Hw' of one head 2' are selected to be wider than the track width Tw. However, if the trace positions of both heads 2 and 2' are shifted so that they overlap somewhat as shown in FIG. 2, the noise position can be placed in the monitor's vertical retrace period, and this does not pose a problem.

Further, when reproducing a still image, the first video head group 1, 1' is used to perform reproduction when the magnetic tape 4 is stopped running, as in the case of recording. Therefore, the locus of the head completely coincides with the recording tracks a and a', and a noise-free still image is obtained.

This embodiment of the apparatus has the advantage that the tape drive system does not require particularly high precision because it records when the tape is stopped during intermittent running. In addition, even when playing back on a conventional VTR, by controlling the tracking adjustment, a playback image with no practical problems can be obtained, and the device can be used for searching, so the merits of this device are great.

As described above, according to the present invention, recording and still image playback are performed during the stop period of the magnetic tape by a pair of video heads mounted at symmetrical positions on the rotating drum with a step difference of one track width, and Since normal playback is performed using another pair of video heads mounted at symmetrical positions on the drum, there is no need for special high precision in the magnetic tape drive system, and furthermore, the above video heads can be set at a predetermined azimuth angle. By providing this, it is possible to perform recording and playback that is compatible with the conventional VHS format or Beta format.

[Brief explanation of drawings]

1a and 1b are diagrams illustrating the arrangement of a video head of a magnetic recording/reproducing apparatus according to an embodiment of the present invention;
FIG. 2 is a diagram for explaining the tape pattern recorded on the magnetic tape by the apparatus and the operation during normal playback. 1, 1'...first pair of video head groups, 2,
2'...second pair of video heads, 3...rotating drum, 4...magnetic tape.

Claims (1)

[Claims] 1. A magnetic recording and reproducing device that enables long-time recording by performing intermittent recording includes a rotating drum placed at a predetermined angle with respect to the magnetic tape, and a rotary drum located on the outer periphery of the rotating drum along its central axis of rotation. A pair of video heads are installed symmetrically with respect to the drum and offset by one track width in the direction of the central axis thereof, and are used for recording and playing still images when the magnetic tape is stopped. 1. A magnetic recording/playback device comprising a pair of video heads for normal playback mounted symmetrically with respect to each other.