Video tape recorder

Details Video tape recorder Video tape recorder

2000-11-30

2004-05-04

Tran, Thai (Department: 2615)

Motion video signal processing for recording or reproducing

Local trick play processing

With randomly accessible medium

C386S349000, C386S349000

Reexamination Certificate

active

06731861

ABSTRACT:

TECHNICAL FIELD
The present invention relates a video tape recorder having a long-time recording mode not less than five times a standard recording mode.
BACKGROUND ART
In recent years, trend towards more inexpensive video tape recorders is gaining momentum and there is a demand for reduction of running cost of a magnetic tape. However, commercially available elongation of recording period has so far advanced to mere recording modes capable of recording for periods two and three times that of a standard recording mode. Hereinafter, the recording modes capable of recording for periods two and three times that of the standard recording mode are, respectively, referred to as a “twofold recording mode” and a “threefold recording mode”. Similarly, recording modes capable of recording for periods four, five and six times that of the standard recording mode are, respectively, referred to as a “fourfold recording mode”, a “fivefold recording mode” and a “sixfold recording mode”.
Hereinafter, a prior art video tape recorder is described. Conventionally, a video tape recorder which enables recording and playback in the sixfold recording mode as the long-time recording mode not less than five times the standard recording mode is known from Japanese Patent Laid-Open Publication No. 7-73405 (1995). This video tape recorder is shown in
FIGS. 3 and 4
. In
FIGS. 3 and 4
which are schematically explanatory of arrangements of rotary heads of the conventional video tape recorder, small circles laid along a large circumference represent the mounted heads. In
FIG. 3
, there are provided a single head pair
5
(
5
R,
5
L) for the standard recording mode having a head width slightly smaller than a double of a track pitch of the threefold recording mode, double azimuth type four heads constituted by a head pair
7
(
7
R,
7
L) for the threefold recording mode having a head width substantially equal to the track pitch of the threefold recording mode and a head pair
6
(
6
R,
6
L) for the sixfold recording mode having a head width slightly smaller than a double of a track pitch of the sixfold recording mode and an audio head pair
4
(
4
R,
4
L) used in all the recording modes.
Hereinafter, functions of the conventional video tape recorder of the above described arrangement are described with reference to Japanese Patent Laid-Open Publication No. 7-73405 (1995). Initially, recording and playback in the standard recording mode and interchangeable playback in the threefold recording mode are performed by the single head pair
5
. Meanwhile, recording and playback in the threefold recording mode are performed by the head pair
7
, while recording and playback in the sixfold recording mode are performed by the head pair
6
for the sixfold recording mode, in which the track width is slightly smaller than the double of the track pitch of the sixfold recording mode and an azimuth angle is so set as to range from ±0° to ±20°. Special playback in the standard, threefold and sixfold recording modes is complemented by a digital circuit employing a field memory.
Then, the arrangement of the heads shown in
FIG. 4
is described. In double azimuth type four heads
1
R,
1
L,
9
R and
9
L, the heads
1
R and
1
L form a head pair E used for recording and playback in the standard recording mode and the heads
9
R and
9
L form a head pair F used for recording and playback in the threefold recording mode. Generally, head widths of the head pairs E and F are so selected as to be about 49 &mgr;m and 26 &mgr;m, respectively. Meanwhile, the heads
8
R and
8
L are provided as a head pair G for recording and playback in the sixfold recording mode. A head width of the head pair G is set to be slightly smaller than a double of the track pitch of the sixfold recording mode. Furthermore, a head pair B constituted by the heads
4
R and
4
L is commonly used for high-fidelity audio recording and playback in the standard, threefold and sixfold recording modes. Generally, in view of interchangeable playback, a track width of the head pair B is so selected as to range from 26 &mgr;m to 30 &mgr;m. Interchangeable playback in the standard and threefold recording modes, recording and playback in the standard recording mode and special playback in both of the standard and threefold recording modes are performed by the head pairs E and F. Meanwhile, during ordinary playback of a track in the threefold recording mode, the head pair G is used such that crosstalk from an adjoining track of the track does not happen.
However, in the arrangement of
FIG. 3
, since during special playback in all the recording modes, it is necessary to provide a digital circuit having a field memory for storing in one field a video signal obtained by subjecting a playback signal output to FM demodulation and a color-under signal, such a drawback is incurred that the burden of cost is heavy as described in Japanese Patent Laid-Open Publication No. 7-73405 (1995).
Meanwhile, since the four heads including the heads having the azimuth angle different from that of prior art and the normal heads for the standard recording mode for the track pitch narrower than that of prior art should be produced additionally, such a problem will arise that the burden of cost is heavy also in view of balance between capital investment and the number of the heads to be produced.
Moreover, in the arrangement of
FIG. 4
, the head pair G for the sixfold recording mode is used as a playback head so as to prevent crosstalk during recording and playback in the threefold recording mode but disadvantageously yields an output lower than that of full-track playback.
Meanwhile,
FIGS. 3 and 4
are common to each other in that recording and playback in the sixfold recording mode are exclusively performed by the heads having the head width slightly smaller than the double of the track pitch of the sixfold recording mode. Since recording and playback are performed by the same heads, such a contradiction is incurred that during recording, the head width should be larger than the track pitch such that an unerased portion of high-fidelity sound is eliminated, while during playback of a track, the head width should be smaller than the track pitch such that crosstalk from an adjoining track of the track is obviated. At the same time, such an inconvenience is also incurred that sound quality of high-fidelity audio is deteriorated extremely or allowance for interchangeable playback of high-fidelity audio signals in the standard or threefold recording mode is lessened excessively. This point is not referred to in Japanese Patent Laid-Open Publication No. 7-73405 (1995).
This point is explained in the sixfold recording mode with reference to FIG.
5
.
FIG. 5
is conceptually indicative of how the heads of the conventional video tape recorder trace recording tracks. P
1
, P
2
, P
3
and P
4
are tracks of high-fidelity sound and video signals in the sixfold recording mode and have a pitch of 9.6 &mgr;m. The tracks P
1
and P
3
have an identical azimuth, while the tracks P
2
and P
4
have an identical azimuth.
The high-fidelity sound tracks and the video tracks do not necessarily coincide with each other but are here set to coincide with each other for simplification of the description. The head pair B is a high-fidelity head pair for performing recording and playback in the standard, threefold and sixfold recording modes and is composed of the heads
4
L and.
4
R in
FIGS. 3 and 4
. Generally, in view of interchangeable playback, a head width of the head B is selected to range from 26 &mgr;m to 30 &mgr;m as described in Japanese Patent Laid-Open Publication No. 7-73405 (1995). Here, the head width of the head pair B is set at 26 &mgr;m. The head pair G is a video head for recording and playback in the sixfold recording mode and is composed of the heads
6
L and
6
R in FIG.
3
and the heads
8
L and
8
R in
FIG. 4. A
head width Twg of the head pair G is set to be slightly smaller than the double of the track pitch of the sixfold recording mode, i.e., less than 19.2 &mgr;m.

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