JPH0474915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement of a helical scan type video tape recorder that enables insert editing recording.

BACKGROUND ART AND PROBLEMS First, the usual recording method of a conventional helical scan type video tape recorder will be explained with reference to FIG. TP indicates magnetic tape, AT,
CT indicates an audio track and a control track formed on the side edges of the magnetic tape TP, respectively. CTL is a control signal recorded on the control track CT corresponding to every other gradient magnetic track. _T1 to _T14 indicate gradient magnetic tracks sequentially recorded one by one in each field of the video signal to be recorded on the magnetic tape TP. These magnetic tracks T ₁ to _{T 14} are alternately recorded one by one by a pair of rotating magnetic heads having different magnetically actuated gaps and arranged at an angle of 180°. The pair of rotating magnetic heads are housed in a tape guide drum. The tape guide drum consists of a fixed lower drum and a rotating upper drum.
A pair of rotating magnetic heads rotate together with the rotating upper drum.

In order to particularly increase the recording density of the magnetic tape TP, the magnetic tracks _T1 to _T14 are recorded so that their side edges overlap one another. If the width of the magnetically operating gap between a pair of rotating magnetic heads is a, and the width of the overlapping side edges of adjacent magnetic tracks is c, then each magnetic track T ₁ recorded on the magnetic tape TP is substantially
The width of ~T ₁₄ is a−c=b. That is, a magnetic track is scanned and recorded from bottom to top in the figure by one rotating magnetic head, and then the magnetic track next to it is scanned and recorded in the figure by the other rotating magnetic head so that it first overlaps the side edge of the magnetic track. When the magnetic track is scanned and recorded from the bottom to the top, the portion of the width c where the previous magnetic track overlaps with the magnetic track after the previous magnetic track is erased.

Now, the operation of insert editing recording in such a helical scan type video tape recorder will be explained with reference to FIG. For example, the first
On the magnetic tracks T ₅ to _{T 10} in the figure, new magnetic tracks T′ 5 to T′ ₅ are created based on the new video signal.
Consider insert editing recording (overlapping recording) at T′ ₁₀ . In FIG. 2, the shaded area shows the magnetic track newly recorded by insert editing.
In this way, the final magnetic track T′ ₁₀ recorded by insert editing is the same as the previously recorded magnetic track T′10.
Since the magnetic track _T11 overlaps with the magnetic track _T11 , both sides of the magnetic track _T'10 and _T12 are overlapped and erased to a large extent, and the effective width d of the magnetic track _T11 becomes 2b-a. I become confused. For example a
If is 33 μm and b is 19 μm, then d will be 5 μm.

Therefore, when playing back the already recorded magnetic track _T11 that overlaps with the last magnetic track of the insert editing record, the S/N of the playback signal (high frequency signal) will be extremely low, so the playback screen will be There is a risk of deterioration of image quality and disturbance of vertical synchronization.

OBJECTS OF THE INVENTION In view of the above, the present invention has a pair of rotating magnetic heads having different magnetically actuated gaps, and in the pair of rotating magnetic heads, the side edges of adjacent magnetic tracks on a magnetic tape are different from each other. A helical tape that records a video signal and performs insert editing recording by overwriting a new magnetic track on the already recorded magnetic track on the magnetic tape using a pair of rotating magnetic heads. The present invention proposes a scan type video tape recorder that can avoid deterioration of the image quality of the playback screen and disturbance of vertical synchronization.

SUMMARY OF THE INVENTION The present invention has a pair of rotating magnetic heads with different magnetically actuated gaps, and the pair of rotating magnetic heads records a video signal on a magnetic tape so that the side edges of adjacent magnetic tracks overlap each other. A helical scan type video tape recorder that performs insert editing recording by overwriting new magnetic tracks on already recorded magnetic tracks on a magnetic tape using a pair of rotating magnetic heads. At the time of insert editing recording, the recording position of at least the final magnetic track of the newly recorded magnetic track is shifted from the already recorded magnetic track, and the final magnetic track overlaps the previously recorded magnetic track. The tracking servo circuit is provided with means for reducing the portion of the data that is erased.

According to the present invention, it is possible to avoid deterioration of the image quality of the reproduced screen and disturbance of vertical synchronization.

Embodiment An embodiment of the present invention will be described below with reference to FIG. In this embodiment, in the helical scan video tape recorder that enables the above-mentioned insert editing recording, the entire recording position of the newly recorded magnetic track is determined at the time of insert editing recording.
By shifting the magnetic track that has already been recorded,
The tracking servo circuit is provided with means for reducing the portion of the recorded track that is already erased by overlapping the final magnetic tracks.

The embodiment shown in FIG. 3 is a case where the present invention is applied to a capstan servo circuit of a video tape recorder. First, the capstan servo circuit CS will be explained. SW ₁ and SW ₂ are recording/reproducing changeover switches, each having a movable contact m, a fixed recording contact r, and a fixed reproducing contact p. During insert editing recording, the movable contact m of changeover switch SW ₁ is switched to the playback side fixed contact p side, and the changeover switch
The movable contact m of SW ₂ is switched to the recording side fixed contact r side.

Hc is a fixed magnetic head for recording and reproducing the control signal CTL (see Figure 4) recorded on the magnetic tape TP, and its coil is a selector switch.
Connected to the movable contact m of SW ₁ . changeover switch
The recording side fixed contact r of SW ₁ is connected to the control signal input terminal 14 . A fixed contact p on the playback side of the changeover switch SW ₁ is connected to the phase comparator circuit 2 .

The recording side fixed contact r of the changeover switch SW ₂ is connected to the input terminal 1 to which a vertical synchronizing signal separated from the video signal to be recorded is supplied. The playback side movable contact p of switch SW ₂ is a 30Hz internal oscillator.
Connected to OSC. The movable contact m of the changeover switch SW ₂ is connected to the phase comparator circuit 2 through a tracking control delay circuit 3. 4 is its tracking control signal input terminal. The output side of the phase comparator circuit 2 is connected to the capstan motor CM via an amplifier 5.

A control circuit 15 described below is connected to the input terminal 4 of the delay circuit 3 for tracking control. The power supply +B is connected through a resistor 6 and further through a capacitor 7 to ground. The midpoint of the connection between the resistor 6 and the capacitor 7 is connected to the collector of a switching transistor 9 through a capacitor 8, and its emitter is grounded. The base of the transistor 9 is connected through a resistor 10 to an input terminal 11 to which an insert edit recording control signal is supplied.

DS is a drum servo circuit, which will be explained below. The output of the movable contact m of the above-mentioned changeover switch SW ₂ is supplied to the phase comparator circuit 12, and the magnetic head Hp that constitutes a pulse generator that generates pulses according to the rotation of a pair of rotating magnetic heads.
A 30Hz output from the phase comparator circuit 12 is supplied to the phase comparator circuit 12. Then, the output of this phase comparator circuit is transmitted to amplifier 1.
3 to a drum motor DM for rotating the pair of rotating magnetic heads together with the upper drum of the tape guide drum.

Note that in these capstan servo circuit CS and drum servo circuit DS, only the phase servo system is shown, and the speed servo system is not shown.

Next, the operation of the circuit shown in FIG. 3 will be explained with reference to FIG. 4 as well. During insert editing recording, the movable contact m of the changeover switch SW ₁ is switched to the playback side fixed contact p, and the changeover switch SW ₂ is switched to the playback side fixed contact p.
The movable contact m is switched to the recording side fixed contact t. Furthermore, since a control signal that is at a high level during the insert editing recording period is supplied to the input terminal 11, the transistor 9 is turned on during that period, and the capacitor 8 is connected in parallel to the capacitor 7. By doing this, the delay amount of the delay circuit 3 is different from the delay amount during normal recording, and as shown in FIG.
The recording positions T' ₅ to T' ₁₀ are recorded shifted to the right in FIG. Therefore, the execution width d of the magnetic track _T11 whose side edge is erased by the recording track _T'10 during the final insert editing recording is larger than 2b-a by Δd. For example, this △d is
3.5μm, so d is 5μm to 8.5μm
spread to In this case, the level of the reproduction signal (high frequency signal) of the magnetic track _T11 increases by about 60%.
Therefore, the S/N of the vertical synchronization signal also improves.
It also improves.

Next, the circuit 15 connected to the delay circuit 3 sets the delay amount to 0, 1, and 1, respectively, with respect to normal recording.
The high frequency signal levels at 2 and 3 mm/sec were 65 mV, 80 mV, 95 mV, and 110 mV, respectively.

In the above embodiment, the entire magnetic track to be recorded by insert editing is shifted, but only the final magnetic track to be recorded by insert editing or from the previous magnetic track to the final magnetic track is shifted. It is also possible to record the images by shifting them by a predetermined amount. In this case, it is necessary to confirm the position of the final magnetic track to be recorded by insert editing.

According to such a helical scan type video tape recorder, the erased portion of the already recorded magnetic track that overlaps with the final magnetic track of the newly recorded magnetic track during insert editing recording is reduced, and as a result, the reproduction signal (High frequency signal) S/N is improved, and image quality deterioration of the reproduced screen and vertical synchronization disturbance are avoided.

Effects of the Invention According to the present invention described above, a pair of rotating magnetic heads are provided with different magnetically operating gaps, and the side edges of adjacent magnetic tracks on the magnetic tape are overlapped with each other in the pair of rotating magnetic heads. A helical scan in which a video signal is recorded on a magnetic tape, and a pair of rotating magnetic heads overwrites and records a new magnetic track on an already recorded magnetic track on a magnetic tape, thereby performing insert editing recording. In a type video tape recorder, the portion of the already recorded magnetic track that is erased by the final magnetic track during insert editing recording is reduced, and the S/
Since N is improved, it is possible to avoid deterioration of the image quality of the reproduced screen and disturbance of vertical synchronization.

[Brief explanation of the drawing]

1 and 2 are pattern diagrams showing recording patterns on a magnetic recording tape during normal recording and insert editing recording in a conventional helical scan video tape recorder, and FIG. 3 is a pattern diagram showing recording patterns on a magnetic recording tape in a conventional helical scan video tape recorder. FIG. 4 is a block diagram showing the main parts of an embodiment of the tape recorder, and FIG. 4 is a pattern diagram showing the recording pattern of the magnetic tape to provide an explanation thereof. TP is a magnetic tape, T ₁ to _{T 14} are already recorded magnetic tracks, T' ₅ to T' ₁₀ are newly recorded magnetic tracks during insert editing recording, CTL is a control signal, and CS is a tracking servo circuit. 3 is a delay circuit for tracking control, and 15 is a control circuit for changing the amount of delay.

Claims (1)

[Claims] 1. A pair of rotating magnetic heads with different magnetically operating gaps are provided, and the pair of rotating magnetic heads records a video signal on a magnetic tape so that the side edges of adjacent magnetic tracks overlap each other, In the helical scan video tape recorder, insert editing recording is performed by overwriting new magnetic tracks on the magnetic tracks already recorded on the magnetic tape using the pair of rotating magnetic heads. At the time of insert editing recording, the recording position of at least the final magnetic track of the newly recorded magnetic track is shifted with respect to the already recorded magnetic track, so that the final magnetic track overlaps with the previously recorded magnetic track. 1. A helical scan type video tape recorder, characterized in that a tracking servo circuit is provided with means for reducing the erased portion of a magnetic track.