JPH0413201A - Video tape recorder - Google Patents

Abstract

PURPOSE:To miniaturize a head cylinder without impairing the interchangeability of a tape format by providing one double-azimuth head as a rotary magnetic head. CONSTITUTION:One double-azimuth head 3 is provided on a miniaturized head cylinder 2 as the rotary magnetic head. Also, the same tape feed speed as that in standard constitution is set, and cylinder rotating speed is double. The time required for one scan is reduced corresponding to difference of a tape winding angle with that in the standard constitution in recording/reproduction, however, a track angle in standstill is set differently from that in the standard constitution, and the format of a tape 1 coincides with that in the standard constitution. Furthermore, recording/reproducing is performed on each track of the tape by compressing/expanding a signal in the recording/reproduction in digital fashion by a time base compression means and a time base extension means in a recording circuit part. In such a way, it is possible to miniaturize the cylinder by providing one rotary magnetic head at the cylinder without impairing the interchangeability of the tape format.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video tape recorder (hereinafter referred to as a VTR) whose head cylinder can be made smaller without impairing tape format compatibility.

[Conventional technology]

Conventionally, in helical scan type VTRs such as 8 mm VTRs and VH5 VTRs, in the standard configuration, the angle of video tape wrapping around the head cylinder (hereinafter referred to as tape wrapping angle) is set to 1800. At the same time, two rotating magnetic heads with opposite azimuths, i.e., the forward and
Two heads of negative azimuth are mounted on the cylinder 180° apart.

Based on the constant speed running of the tape and constant speed rotation of the cylinder, both heads alternately helically scan the tape every half rotation of the cylinder, and one field's worth of video signals is recorded on each track of the tape. .

will be played.

By the way, in order to reduce the size of VTRs, VH and S type VTRs use VTRs that are smaller than the so-called full cassette.
VHS compact VTR (pJ lower C type VT) which uses H5, C cassette to reduce the cylinder diameter.
R) was invented.

This C type VTR is, for example, one of the articles in the magazine "Television Technology".
As described in October 1983 issue, 9 pages 54-55 (published by Denshi Gijutsu Publishing Co., Ltd.), tape wrapping is
70°, the cylinder is provided with four heads of positive azimuth, negative azimuth, positive azimuth, and negative azimuth at 90° intervals, and the rotational speed of the cylinder is increased from 3 Orpm to 45 rpm.

Then, the tape is sequentially helically scanned by the four heads, and the entire video signal and the like for one field are recorded and reproduced as they are on each one of the tapes.

At this time, the tape winding angle and cylinder rotation speed are both twice that of the standard configuration, so the tape 7 Ohmanoto is the same as the standard configuration, and the cylinder diameter can be reduced without compromising tape format compatibility. is planned.

[Problem to be solved by the invention]

In the case of the conventional C type VTR, in order to reduce the diameter of the cylinder, two positive azimuth heads and two negative azimuth heads are required, making it expensive, and the crosstalk characteristics between channels deteriorate due to head switching. There is a problem in that the image quality characteristics of recording and reproduction deteriorate as the size increases.

In order to reduce the diameter of the head cylinder in an 8 mm type VTR, if the head cylinder is constructed in the same manner as the conventional C type VTR, problems similar to those described above will occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a VTR 1 in which only one rotary magnetic head i is provided to completely reduce the diameter of the head cylinder.

[Means to solve the problem]

In order to achieve all of the above objects, in the VTR of the present invention, one double azimuth head as a rotating magnetic head is installed in a head cylinder with a reduced diameter, the degree is doubled, and the track angle at rest is set to the standard configuration. Time axis compression in which the tape format is the same as the standard configuration, and the recording circuit unit compresses the recording signal for each one track in the standard configuration into one scan length of the double azimuth head. The reproduction circuit section is provided with time axis extension means for digitally extending and restoring the reproduction signal of the double azimuth head.

[Effect]

In the VTR of the present invention constructed as described above, one double azimuth head is provided as a rotating magnetic head in a head cylinder having a reduced diameter.

In addition, the tape running speed is set as in the standard configuration,
The cylinder rotation speed is set to double.

With the above settings, the tape winding time during recording and playback will be shorter depending on the difference in angle from the standard configuration, but the trunk angle at rest (cylinder lead angle)
is different from the standard configuration, and the tape format is the same as the standard configuration.

Further, the time axis compressing means of the recording circuit section and the time axis expanding means of the reproducing circuit section digitally compress and expand the signals during recording and reproduction, and record and reproduce them on each track of the tape.

Therefore, the size of the cylinder can be reduced by providing one rotary magnetic head (m1) in the Norinta without compromising tape format compatibility.

〔Example〕

One embodiment will be described with reference to FIGS. 1 to 6.

In this embodiment, it is applied to an 8 mm VTR, and as shown in Fig. 1, the video tape t1) is wound around the head cylinder (2) at a corner (the tape is wound at a corner) at a angle of 180 mm in the standard configuration. ° to 2700 (3
/2 times).

In addition, the diameter (cylinder diameter) of the cylinder (2) is set to 27- (2y3 times) smaller than +40 in the standard configuration, and this cylinder (2) has a positive azimuth head, a negative azimuth head, that is, the A head (3a), One double azimuth head with integrated B head (3b)' + 3 + Issei Kel.

Furthermore, the tape speed is set to be the same as in the standard configuration, the cylinder rotational speed is set to double that in the standard configuration, and the track angle (cylinder As will be described later, the tape format is made the same as in the standard configuration, except that the tape format is the same as in the standard configuration.

In other words, in the standard configuration of an 8mm VTR,
As shown in Fig. 2(a), the video tape (l)' is wrapped around the head cylinder (2) by 180 degrees and travels, and the cylinder f2i' (7) 18 (at a position separated by 1° lI) To A, do (3a) tB head (3b)' are provided.

Then, the A head (3a)' and the B head (3b)' alternately scan the tape every half rotation of the cylinder + 2 l.
Each track of Cheebuoy records 1 field (1/60 second) video signal, audio signal, biloft signal, etc.

will be played.

In place of the cylinder (2) in FIG. 2(a), a head cylinder having a diameter 273 times that of the cylinder (2) is provided,
Tape format compatibility? In order to perform recording and playback without loss, as shown in the same figure (b), the ℃ type V
It is conceivable to configure it in the same way as TR.

In FIG. 2(b), the videotape fi+ is wrapped around the head cylinder (2) for 270 degrees and travels, while the cylinders (2 [Ni A head (3a)', B head (3a)',
3bf, A head (3aj, B head (3bf') are provided at 90° intervals.

Furthermore, the cylinder diameter of cylinder (2) in FIG. 2(a).

The rotational speed, tape speed, and track angle when stationary and when running are set to R, ND, VT, and θ0. If θ is the cylinder diameter of cylinder (2) in the same figure (b), the rotational speed is 9, the tape speed and the track angle at rest and when running are i R, ND-V7' and θ〇-2θ, then the tape formats are compatible. In order to improve the performance, R'-2R,
Np' = = ND, ■1 = vT, θO (θ0.i = θ Ni setting.

In the case of (in Figure 2), instead of reducing the cylinder diameter by 100 times, the tape winding is square and the tape speed is doubled, so that four heads (3a) to (3b)
each scans the tape for a period of one field and
All signals for one field are recorded and reproduced, and the tape format becomes the same as that shown in FIG. 2(a).

On the other hand, in FIG. 1, if the cylinder diameter 9 rotational speed of cylinder (2), the tape speed, and the track angle when stationary and when running are i, ND, V-r', and θ0-〆, then k/=
Period □ Scan! I! Recording and reproduction are performed with the same track length L (=20π) as in the case of FIG. 2(a).

At this time, set the trace states of the heads (3a) and (3b) to satisfy the condition No. 1, set θ = θ, and make the entire tape track format the same as that shown in Figure 2 (a) to ensure format compatibility. We aim to

Furthermore, as described above, the head (3a) is used during recording and reproduction.

In order for (3b) to scan for a period that is twice as long as one field (= 1/day = yo seconds), the recording circuit section and the reproducing circuit section are configured as shown in Figs. 3 and 5 using digital memory. .

That is, in the recording circuit section, for example, the composite video signal of every field (=1/60 second) of the input terminal (4) shown in A in FIG. The luminance signal (Y signal) and color signal (
The Y signal is input to the modulation circuit (7) via a Y signal processing circuit (6) such as an encoder assist circuit.

Then, the modulation circuit (7) transmits the Y signal to the sync chip at 4.2MHz, IQQ% white level J/f 5.4.
The signal is modulated into an FM signal of MHz, and the output signal of the modulation circuit (7) is supplied to the mixing circuit (8).

In addition, the C signal is processed by a C signal processing circuit such as the 127797 circuit (
9: The signal is supplied to the low frequency conversion circuit 110H through the converter circuit (10), frequency converted to a low frequency by this conversion circuit (10), and then supplied to the mixing circuit (8).

Furthermore, the audio signal of the input terminal (river) on the same time axis as the video signal of the input terminal (4) is supplied to the modulation circuit (13) with a carrier frequency of 1.5 MHz via the noise reduction circuit 021, and this modulation circuit converts the FM Modulated and mixed circuit (8)
supplied to

Then, the modulation circuit (71e 03
) and the output signal and input terminal 0 of the low frequency conversion circuit (10)
The pilot signals for tracking control (ATF) in 4) are frequency multiplexed and synthesized, and the V
A signal constituting one field is formed in 1760 seconds, which is the same as the TR recording signal, and this signal is sent to the A/D conversion circuit 0.
6).

On the other hand, the frequency fsc (358MHz) included in the C signal
The color subcarrier signal of is detected by the fsc detection circuit i16+, and the fsc output signal of this detection circuit 06) is supplied to the first clock generation circuit 17F consisting of a borrowed PLL circuit, and A/D conversion circuit (
15j g 2nd clock generation circuit consisting of a borrowed PLL circuit (181 has a frequency of 3 fscC158MH
A first clock signal of zx3=10.7 MHz) is provided.

The A/D conversion circuit (in which the number of quantization bits is set to about 6) converts the input signal into a digital signal using the first clock signal as a sampling clock, and converts this digital signal into a channel switching switch ( 19).

Further, the vertical synchronization signal included in the Y signal is detected by the vertical synchronization detection circuit 20, and this detection circuit (based on the detection signal of 20°, the switching pulse generation circuit! 21)
All field switching pulses that are inverted at a timing before H (H is a horizontal scanning period) are formed.

This field switching pulse causes the switch (19) to switch for each field. For example, the digital signal for one odd field is stored in the digital memory (22a).
At the same time, the digital signal for one even field is stored in the digital memory (22b).

In addition, both memories (22a) and (22b) are each (
The capacity is set to 3fsc×6 bits)/60=1.07 Mbits.

The digital signals in the memories (22a) and (22b) are converted into analog signals by D/A conversion circuits (23a) and (23b), and then supplied to recording amplifiers (24a) and (24b).

At this time, the digital signal for one field stored in each of the memories (22a) and (22b) is transferred to the head (
3a).

(3b) Tape il with each 1740 second scan
+, the frequency 12fSC second clock signal of the clock generation circuit (18) is 173 in the branch circuit r2.
a sampling clock with a frequency of 4 fsc,
In other words, a clock having a frequency that is one times that of the sampling clock is generated.

Then, the sampling clock of the disconnection of the branch circuit is supplied to the D/A conversion circuits (23a) and (23b), and both conversion circuits (23a) and (23b) convert the / IJ (22a), (22b) D1/6
The digital signal of Rota 1 field written in 0 seconds is 178
It is read out in 0 seconds and converted to analog.

Through this analog conversion, the time axis of the original video signal, audio signal, etc. is compressed by 374 times.

The output signal of 1% conversion (23a, (23b)) is sent to recording amplifiers (24a), (24b) and rotary transformer (26a).

(26b)' to y F (3a), (3b)
11 is supplied and recorded on tape i11 in the same format as in the standard configuration.

Next, in the reproduction circuit section, A in FIG.

Heads (3a) and (3b) shown in B (D I/80 seconds each) playback signals for one track are transmitted to transformers (26a) and (3b).
26b), and are supplied to A/D conversion circuits (28a) and (28b) having the same number of quantization bits as the conversion circuit (15) in FIG. 3 via reproduction amplifiers (27a) and (27b).

In addition, since the sampling clocks of the A/D conversion circuits (28a) and (28b) are formed by following the reproduction jitter, the output signal of the reproduction amplifier (27b) is
This filter is supplied with ゜! 29) extracts a component 100 times the horizontal scanning frequency fH in the pilot signal, that is, a single frequency component called frequency f4.

Furthermore, the output signal of the band Pannu filter (29) is PL
The clock signal is supplied to a write clock generation circuit which is a combination of an L circuit and a branch circuit, and this generation circuit forms a write clock signal having a frequency f4 6374 times (=4fsc) synchronized with the reproduced signal.

Then, conversion circuits (28a) and (28b) convert the reproduced signal into a digital signal using the clock signal between the clock generation circuits as a sampling clock.

Further, based on the clock signal of the clock generation circuit example, the digital signals of the conversion circuits (28a) and (28b) are written and stored in the digital memories (31a) and (31b).

Furthermore, the digital signals of the memories (31a) and (31b) are sent to D/A via the switch (to) 4 for field synthesis.
A signal similar to the output signal of the mixing circuit (8) in FIG. 4 is formed by analog conversion between the converter circuits (3) and (3).

At this time, the total jitter of the digital signal of one track accumulated in the memories (31a) and (31b) is corrected to restore the original 17
In order to return to 60 seconds, a clock signal for reading out the memories (31a) and (31b) is generated using a clock signal from a reference clock generation circuit having a crystal oscillator configuration that controls the rotation of the cylinder (2).

That is, the clock signal of the example generator circuit is set to 374 times (=3fsc) the clock signal for writing, and based on this clock signal, the memory (3ta), (31b)
At this time, the digital signal of B in FIG. 6 is read out.

As shown in C, the digital signal for one track played at 1/80 seconds is read out in 1760 seconds, and the time axis is 473 seconds.
is expanded to.

Moreover, since a clock signal from a stable oscillation circuit is used, fluctuations due to reproduction jitter are compensated for, so-called TBC (
A Time Ba5e Corrector) circuit is formed.

Then, the digital signals read from the memories (31a) and (31b) are synthesized by switching the switch (6) every 1/60 seconds, and then, based on the clock signal of the generation circuit example,
It is converted into a continuous analog signal by a conversion circuit (33).

Further, the output signal of the conversion circuit (33) is frequency-separated by a separation circuit having a filter structure, as in the case of a conventional 8 mm VTR.

And Y signal processing circuits such as demodulation circuit t36+ and de-emphasis circuit! 37), the Y signal included in the output signal of the separation circuit Gen is regenerated, and the frequency conversion circuit 138j
The eC signal processing circuit (39) reproduces the C signal included in the output signal of the separation circuit +35i.

Further, the processing circuit string, the Y signal of f39j, and the C signal are synthesized by a mixing circuit 140) to form a composite video signal that is the same as the video signal of the input terminal (4) in FIG. is output to.

Also, the demodulation circuit 2. The noise reduction circuit (43) reproduces the audio signal included in the output signal of the separation circuit, and this audio signal is output to the output terminal (fence).

Furthermore, the pilot regeneration circuit (451)
The pilot signal included in the output signal of IIF5 is regenerated, and a tracking control signal based on this regeneration is output to the output terminal (46j).

Then, due to the above time expansion, the output terminal t41i,
The +44° video signal and audio signal are returned to the same time axis as A in FIG.

Therefore, with a simple configuration in which one double azimuth head (3) is provided on the cylinder i2+, which has a smaller diameter than the conventional cylinder, recording and reproduction can be performed with the format of the tape +I) being the same as that in the standard configuration.

Further, head switching is reduced, and deterioration of crosstalk characteristics between channels such as rotary transformers (26a) and (26b) based on head switching is suppressed, thereby preventing deterioration of image quality characteristics in recording and reproduction.

Moreover, the memo 'J (31a), (31b) of the regeneration circuit section
), the fluctuations due to reproduction jitter are compensated for and the deterioration of image quality characteristics is further suppressed.

In addition, since the format of the tape is the same as the standard configuration, the recorded tapefl)z-8mm VT of the standard configuration
It can be played in R, and the standard configuration of 8j
It is also possible to play back tapes recorded with an IJVTR.

The diameter of the cylinder (2), the tape wrapping, the corners, etc. are not limited to those in the embodiment.

Furthermore, in the above embodiment, it was applied to 821JVTR, but
Of course, the present invention can be applied to VTRs using the Heri-Carnecan system.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

One double azimuth head is provided on the hemlock ring, which has a smaller diameter than in the standard configuration, the tape running speed is set to be the same as in the standard configuration, and the cylinder rotation angle is set to twice that in the standard configuration.

The time for each scan of the head during recording and playback will be longer depending on the difference in tape winding angle from the standard configuration, but the track angle (cylinder lead angle) when stationary is different from the standard configuration. , the tape format will be the same as in the standard configuration.

Further, the time axis compressing means of the recording circuit section and the time axis expanding means of the reproducing circuit section digitally compress and expand the signals during recording and reproduction, and record and reproduce them on each trunk of the tape.

Therefore, it is possible to reduce the size of the cylinder with an inexpensive configuration in which only one rotating magnetic head is installed in the cylinder without compromising tape format compatibility. It is possible to reduce the diameter of the cylinder without deterioration due to the reduction in the diameter of the cylinder, and to prevent deterioration of image quality characteristics during recording and reproduction.

[Brief explanation of drawings]

The drawings show one embodiment of the video cheap recorder of the present invention, and FIG. 1 is an explanatory diagram of the tape winding corner and head arrangement;
Figures 2 (a) and (b) are explanatory diagrams of the tape winding corners and head arrangement in the standard configuration and in the 4-head configuration. Figures 3 and 4 are block diagrams of the recording circuit section and explanation of operation. Figure 5. Timing chart for . FIG. 6 is a block diagram of the reproducing circuit section and a timing chart for explaining the operation. +1+ ・Video tape, (2)...head cylinder, (3) double azimuth head, (15) t (28
a) t(28b) , A/D conversion circuit, (22a
), (22b), (31a), (31b) −= Te;
9 memory, (23a), (23b) = 3a+,
,, D/A conversion circuit.

Claims (1)

[Claims] (1) Set the wrapping angle of the videotape around the head cylinder to 1
The winding angle is made larger than 80°, and the cylinder rotational speed is made faster than in the standard configuration in which the wrapping angle is 180°,
A video tape recorder in which the cylinder is made smaller than the standard configuration in which the tape is helically scanned for recording and reproduction by a rotating magnetic head provided on the cylinder, and one track of the tape is helically scanned every half rotation of the cylinder. In this, one double azimuth head is provided as the rotating magnetic head, the tape speed during recording and reproduction is the same as that in the standard configuration, the cylinder rotational speed is doubled as in the standard configuration, and the track angle when stationary is The format of the tape is the same as that in the standard configuration by making the format different from that in the standard configuration, and the recording circuit unit is configured to time-base compress the recording signal for each one track in the standard configuration into one scan length of the double azimuth head. 1. A video tape recorder comprising: a time-base compression means for digitally extending and restoring a reproduced signal from the double azimuth head;