JPH041555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video tape recorder, and in particular, an object of the present invention is to provide a video tape recorder that can improve the quality of reproduced sound.

In general, in video tape recorders, especially consumer video tape recorders, audio signals are recorded and played back using a fixed magnetic head that superimposes a high frequency bias on an audio track provided at the end of the magnetic tape in the tape width direction. are doing. However, in the video tape recorder mentioned above, the wow/flatter is 0.2%, the frequency characteristic of the reproduced audio signal is about 12kHz in the high range, and the S/N ratio is 42%.
It was about ~43dB, and the playback quality was not very good.

The present invention solves these conventional drawbacks, and uses first and second magnetic heads attached to a rotating cylinder to perform normal recording and reproduction of video signals. The apparatus is configured to record and reproduce a carrier wave frequency-modulated with an audio signal using third and fourth magnetic heads for reproduction.

The present invention will be described below with reference to drawings of embodiments. FIG. 1 shows an embodiment of the present invention,
In the figure, 1 is a rotating cylinder, and a pair of magnetic heads 3, 6 and 2, 5 are placed at 180 degrees different positions.
is installed. These pairs of magnetic heads 3, 6 and 2, 5 have respective gap positions.
The magnetic heads 2 and 3 which are different by 180 degrees are used as one set, and the magnetic heads 5 and 6 are used as one set. And these one set of magnetic heads 2, 3 and 5, 6
are appropriately selected and used for recording and reproducing video signals and recording and reproducing audio signals in each mode of the video tape recorder. Hereinafter, the pair of magnetic heads 2, 3 and 5, 6 will be referred to as a video head or an audio head depending on the usage situation, since they are appropriately selected and used for video signals or audio signals. Here, the magnetic heads 3 and 6 have head gaps 3a and 6a having the same head track width and different gap inclinations, and the magnetic head 5 has a head track width smaller than that of the magnetic head 6. The magnetic head 2 has a head gap 5a having the same inclination as the head gap 3a of the magnetic head 3, and the magnetic head 2 has a head gap 5a having a head track width larger than that of the magnetic head 6 and a head gap having the same inclination as the head gap 6a of the magnetic head 6. It has 2a. The rotary cylinder 1 rotates in the direction of arrow B in the figure, and records video and audio signals on the magnetic tape 4 running in the direction of arrow A in the diagram, and also records video and audio signals recorded on the magnetic tape 4. Reproduce. At this time, the magnetic tape 4 is wound around the outer periphery of the rotary cylinder 1 by guide rollers 16 and 17 at an angle slightly larger than 180 degrees and tilted at a predetermined angle with respect to the rotation axis of the rotary cylinder 1. .

In such a configuration, in the case of normal recording, video signals are recorded on the magnetic tape 4 running in the direction of arrow A by the video heads 2 and 3 attached to the rotary cylinder 1, and during playback, the video signals are recorded on the magnetic tape 4 running in the direction of arrow A. The video signals recorded by the video heads 2 and 3 are played back by the respective video heads 2 and 3,
The image is processed by a video signal processing system (not shown) and can be viewed on a monitor television. In the case of long-term recording, the video heads 5 and 6 attached to the rotary cylinder 1 record video signals in the same way as the video heads 2 and 3, and the same video heads 5 and 6 play back the video signals during playback. When the running speed of the magnetic tape 4 is slowed down for long-term recording, the track on which the video signal is recorded becomes narrower, so video heads 5 and 6 with narrow track widths for long-term recording are used.
are using. By the way, video head 2,
The azimuths of head gaps 3, 5, and 6 are tilted as shown in Figure 2 (which shows an expanded view of the cylinder viewed from the outside). video head 2
If 3 and 3 are used, the azimuth will be different, so the adjacent track will be played back and a shaky image will be played back. Therefore, video heads 2 and 6 with the same azimuth are used during special playback. In the case of special reproduction of a signal recorded for a long time, the video heads 3 and 5 are used for special reproduction for the same reason.

Next, recording and reproduction of audio signals will be explained. Since the head gap between magnetic heads 2 and 5 is only about 0.5 mm apart, magnetic head 5 traces over the track recorded by magnetic head 2. Magnetic heads 3 and 6 have a similar relationship. Therefore, when recording video signals normally on video heads 2 and 3, audio head 5
and 6 records a carrier wave frequency-modulated with an audio signal. When the recording level of the carrier wave is increased,
This will attenuate the previously recorded video signal.
The recording current of the carrier wave, the reproduction C/N of the carrier wave is 10
The value is selected to be dB. In this case, the amount of attenuation of the video signal is 0.5 dB or less, and there is almost no deterioration of the video. FIG. 3 shows a block diagram of the audio circuit.
The audio signal applied to the input terminal 7 is amplified by the amplifier 8, and then is converted to 1.8M by the modulator 9 composed of PLL etc.
Frequency modulate the carrier wave tuned to Hz. The output of this modulator 9 is applied to a rotary transformer 11 via a switch circuit 10, transmitted to the rotary cylinder 1 side, and applied to audio heads 5 and 6. The audio heads 5 and 6 are located at the positions described above, and since the carrier wave is a temporally continuous signal, the audio carrier wave is recorded superimposed on the video signal. During reproduction, the carrier waves reproduced by audio heads 5 and 6 pass through a rotary transformer 11, and a switch circuit 10 switches between the audio head 5 side and the audio head 6 side so that the output of the head on which the carrier wave is being reproduced is obtained. selected, amplifier 1
It is amplified by 2. The carrier wave amplified by the amplifier 12 is demodulated by the demodulator 13 composed of a PLL etc.
If the audio signal is amplified by the amplifier 14, the audio signal applied to the input terminal 7 can be obtained at the output terminal 15. During reproduction, the audio heads 5 and 6 also reproduce the video signals recorded by the video heads 2 and 3, respectively, but since the azimuths of the magnetic heads 2 and 5 and 3 and 6 are different, the signals are attenuated. This attenuation is 20×log ₁₀ π×W×tanθ/λsin/π×W×tanθ
/λ (dB) where W: track width θ: angular difference λ: It is known that it is expressed by recording wavelength, but the amount of attenuation changes depending on the frequency, track width, and azimuth angle difference, and the audio carrier wave has a video signal. Although it is a frequency band that is also used, it uses 1.8MHz, so
Attenuation of 30dB or more has been obtained. If it is attenuated to this extent, there will be almost no effect, and the audio S/N will be
55dB, frequency characteristics can be obtained from 20Hz to 20kHz. The audio carrier waves reproduced by the video heads 2 and 3 are also attenuated for the same reason, and the video deterioration is less than 1 dB.

During normal playback, audio heads 5 and 6 are used for audio as described above, and during special playback such as still image playback, there is no need to output audio, so video heads 5 and 6 can be switched and used for video playback. Since there is no need to add a separate magnetic head for audio and therefore no need to newly install a rotary transformer, it is also advantageous in terms of cost. If an audio signal is also recorded on the audio track provided at the end of the conventionally used magnetic tape, nothing will happen when the magnetic tape recorded with the device of this embodiment is played back with a conventional video tape recorder. It is possible to maintain compatibility without any influence.

Note that in the above explanation, video heads 2 and 3 are
After recording the video with the audio head 5,
In Section 6, we explained how to record the audio carrier wave, but by swapping the positions of video head 2 and audio head 5, and video head 3 and audio head 6, recording the audio carrier wave with audio heads 5 and 6, and recording the recorded portion. A similar effect can be obtained by recording video signals in video heads 2 and 3 in addition to the above. However, in this case, the recording level of the audio carrier wave recorded by the audio heads 5 and 6 must be increased because it is attenuated by the video signal.

As described in detail above, according to the present invention, the carrier wave is frequency-modulated with an audio signal using the third and fourth magnetic heads for long-term recording and reproducing of video signals provided on a rotating cylinder during normal recording and reproducing. Since the configuration is configured to record and play back the audio signal, it is possible to record and play back the audio signal.
It has the advantage that wow and flutter during reproduction can be increased by more than one order of magnitude, that the S/N ratio can be made good and the frequency characteristics can be improved, and that the reproduced sound quality can be improved. Furthermore, since a magnetic head for long-term recording and reproducing of video signals provided on a rotating cylinder is used for recording and reproducing audio signals, there is no need to add a separate magnetic head and compatibility with conventional video tape recorders can be maintained. It is also possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a rotating cylinder section showing an embodiment of the video tape recorder of the present invention, Fig. 2 is a block diagram of the arrangement of the magnetic head of the rotary cylinder, and Fig. 3 is a block diagram of the audio circuit of the tape recorder. It is a diagram. 1... Rotating cylinder, 2, 3, 5, 6... Video head, 4... Magnetic tape, 16, 17... Tape guide.

Claims (1)

[Scope of Claims] 1. First and second magnetic heads whose head gaps for normal recording and reproduction of video signals attached to a rotating cylinder are tilted in opposite directions, and head gaps for long-term recording and reproduction of video signals are tilted in opposite directions to each other. The first and third magnetic heads and the second and fourth magnetic heads having opposite inclinations of the head gap are installed in close proximity to each other, and
The mounting heights of the first to fourth magnetic heads are made substantially the same so that the recording trajectories of the first and third magnetic heads and the second and fourth magnetic heads on the magnetic tape overlap,
A video tape recorder configured to use third and fourth magnetic heads to record and reproduce carrier waves frequency-modulated with audio signals during normal recording and reproduction. 2. The video tape recorder according to claim 1, wherein the carrier wave of the audio signal has a frequency set to a band where the video signal exists and is recorded continuously in time.