JP2911145B2 - Video tape recorder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a video tape recorder (hereinafter, referred to as VTR) capable of reducing the size of a head cylinder without deteriorating tape format compatibility.

[Conventional technology]

Conventionally, in a helical scan type VTR such as an 8 mm VTR and a VHS VTR, the winding angle of a video tape to a head cylinder (hereinafter referred to as a tape winding angle) is set to 180 ° in a standard configuration. In addition, two rotating magnetic heads of opposite azimuth, that is, two heads of positive and negative azimuth are provided at 180 ° apart from each other in the cylinder.

Based on the constant speed running of the tape and the constant speed rotation of the cylinder, both heads alternately perform helical scanning of the tape every half rotation of the cylinder, and record and reproduce video signals for one field on each track of the tape. Is done.

By the way, in order to reduce the size of the VTR, the VHS type VTR uses a VHS / C cassette smaller than a so-called full cassette to reduce the cylinder diameter.
The S compact VTR (hereinafter referred to as C type VTR) has been invented.

This C-type VTR is, for example, 1983
As described in the October issue, pp. 54-55 (published by Electronic Technology Publishing Co., Ltd.), the tape wrap angle was set to 270 °, and the cylinders were provided with positive azimuth, negative azimuth, and positive azimuth at 90 ° intervals. And four heads of negative azimuth, and the rotational speed of the cylinder is increased from 30 rpm to 45 rpm.

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

At this time, the tape winding angle and the rotation speed of the cylinder are both 3/2 times that of the standard configuration, so the tape format is the same as the standard configuration, and the cylinder diameter can be reduced without compromising the tape format. Is achieved.

[Problems to be solved by the invention]

In the case of the conventional C-type VTR, two positive azimuth heads and two negative azimuth heads are required to reduce the diameter of the cylinder, and the number of heads increases to increase the cost. There is a problem in that the deterioration of the talk characteristics is increased and the image quality characteristics of recording and reproduction are deteriorated.

Even in the case of a VTR of the 8 mm type or the like, if the same configuration as that of the conventional C type VTR is used in order to reduce the diameter of the head cylinder, the same problem as described above occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a VTR in which the diameter of a head cylinder is reduced without increasing the number of heads.

[Means for solving the problem]

In order to achieve the above object, in the VTR of the present invention, two rotating magnetic heads having opposite azimuths are provided at positions 180 ° apart from each other in a head cylinder having a small diameter, and a tape speed during recording and reproducing is set. The same cylinder rotation speed as in the standard configuration where the diameter of the head cylinder is not reduced, the track angle at rest is different from that in the standard configuration, the format of the tape is the same as in the standard configuration, and a recording circuit. A time axis extending means for extending the recording signal for each track in the standard configuration to one scan length of each of the two rotating magnetic heads, and a reproducing circuit for reproducing signals of each of the two rotating magnetic heads. A time axis compression means for digitally compressing and restoring the time axis.

[Action]

In the case of the VTR of the present invention configured as described above, two heads are provided 180 ° apart from each other in the head cylinder having a small diameter, as in the standard configuration, and the tape traveling speed and
The cylinder rotation angle is set as in the standard configuration.

The time for each scan of both heads during recording and reproduction becomes longer in accordance with the difference in tape wrap angle from the standard configuration, but the track angle at rest (cylinder lead angle) differs from the standard configuration. The format of the tape is the same as in the standard configuration.

Further, a signal at the time of recording and reproduction is digitally expanded and compressed by a time axis expansion unit of the recording circuit unit and a time axis compression unit of the reproduction circuit unit, and is recorded and reproduced on each track of the tape.

Therefore, the size of the cylinder can be reduced by providing two heads in the cylinder without deteriorating the compatibility of the tape format.

〔Example〕

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

In this embodiment, the present invention is applied to an 8 mm system VTR, and as shown in FIG. 1, the winding angle (tape winding angle) of the video tape (1) around the head cylinder (2) is set to the standard configuration.
Change from 180 ゜ to 270C ゜ (3/2 times) similar to the C-type VTR.

The cylinder (2) diameter (cylinder diameter) is set to 27 mm (2/3 times) smaller than the standard configuration (40 mm), and the cylinder (2) is set 180 ° away from the standard configuration. Similarly, two rotating magnetic heads of a positive azimuth and a negative azimuth, that is, an A head (3a) and a B head (3b) are provided.

Further, the tape speed and the cylinder rotation speed are set to be the same as those in the standard configuration, and the track angle (lead angle of the cylinder) when the tape (1) is stopped and running around the cylinder (2) at rest is described later. Make the tape format the same as the standard configuration, different from the standard configuration.

In other words, in the standard configuration of the 8mm VTR,
As shown in FIG. 2 (a), the video tape (1) 'runs while being wound around the head cylinder (2) "by 180 [deg.], And the A head (3a) is positioned 180 [deg.] Away from the head cylinder (2)". ) ', B head (3b)'.

The head A (3a) 'and the head B (3b)' scan the tape alternately every half rotation of the cylinder (2) ", and each track of the tape (1) 'has one field (1/60 second). Video signal, audio signal, pilot signal, etc. are recorded and reproduced.

In place of the cylinder (2) 'in FIG. 2 (a), a head cylinder having a diameter 2/3 times that of the cylinder (2)' is provided to perform recording and reproduction without impairing the compatibility of the tape format. Therefore, as shown in FIG. 2B, it is conceivable that the configuration is the same as that of the C type VTR.

In FIG. 2 (b), a video tape (1) "
270 mm is wound around the head cylinder (2) "and the A head (3a)", the B head (3b) ", the A head (3a) and the B head (3b) are 90ら れ る Provided at intervals.

Further, the cylinder diameter of the cylinder (2) 'of FIG. 2 (a), the rotational speed, the tape speed and at rest, the track angle during traveling R, N _D, V _T and theta _O, and theta, FIG ( Bore size of cylinder (2) "of b), the rotational speed, when the tape speed and still, a track angle during traveling _{R, N D ', V T} ' When and θ _{O ',, θ',} the tape format For compatibility, as in the case of C type VTR, V _T ′ = V _T , θ _O ′ = θ _O , and θ ′ = θ.

In the case of FIG. 2 (b), instead of reducing the cylinder diameter to 2/3 times, the tape winding angle and the tape speed are reduced.
By increasing by 3/2 times, four heads (3a) "~
(3b) scans the tape for one field and records and reproduces signals for one field, respectively, and the tape format is the same as that in FIG. 2 (a).

On the other hand, the cylinder diameter of the cylinder (2) in the case of FIG.
Rotational speed, the tape speed and at rest, the track angle during traveling _{R ", N D", V} T " and theta _O", when the theta ", as described above By setting N _D ″ = N _D , V _T ″ = V _T , the head (3
(a) and (3b) scan the tape for a period of 3/2 times of one field and scan the tape for the same track length L (= 20) as in FIG. 2 (a).
π) is recorded and reproduced.

At this time, since the trace state of the heads (3a) and (3b) is shifted from the case of FIG. 2 (a), θ _O ″ is Is satisfied, θ ″ = θ, the track format of the tape is made the same as in FIG. 2A, and compatibility of the format is achieved.

Furthermore, as described above, the head (3a),
(3b) is 3/2 times as long as one field For scanning, the recording circuit unit and the reproducing circuit unit are configured using digital memories as shown in FIG. 3 and FIG.

That is, in the recording circuit section, for example, the composite video signal at the input terminal (4) shown by the waveform A in FIG. 4 is converted into a luminance signal (Y signal) and a color signal by a Y / C separation circuit (5) comprising a comb filter or the like. The Y signal is separated into a signal (C signal) and input to a modulation circuit (7) via a Y signal processing circuit (6) such as an emphasis circuit.

Then, the modulation circuit (7) modulates the Y signal into an FM signal having a sync chip of 4.2 MHz and a 100% white level of 5.4 MHz, and the output signal of the modulation circuit (7) is supplied to the mixing circuit (8). .

Further, the C signal is supplied to a low-frequency conversion circuit (10) via a C signal processing circuit (9) such as an emphasis circuit, and the conversion circuit (10) frequency-converts the low-frequency signal into a low-frequency signal to mix the signal (8). Supplied to

Further, the audio signal of the input terminal (11) on the same time axis as the video signal of the input terminal (4) is output from the noise reduction circuit (1).
The signal is supplied to a modulation circuit (4) having a carrier frequency of 1.5 MHz via 2), and is FM-modulated by the modulation circuit and supplied to a mixing circuit (8).

Then, the modulation circuits (7) and (1) are mixed by the mixing circuit (8).
3) and the output signal and input terminal (1
4) The pilot signal for tracking control (for ATF) is frequency-multiplexed and combined to form a signal that constitutes one field for 1/60 second, which is the same as the recording signal of the conventional 8 mm system VTR. This signal is supplied to the A / D conversion circuit (15).

On the other hand, a chrominance subcarrier signal of frequency fsc (3.58 MHz) included in the C signal is detected by the fsc detection circuit (16), and the output signal of fsc of this detection circuit (16) is output from the PLL circuit for multiplying by six. And a second clock generation circuit (18) comprising an A / D conversion circuit (15) and a PLL circuit for multiplying the frequency by 6 fsc.
A first clock signal (3.58 MHz × 6 = 21.5 MHz) is supplied.

The A / D conversion circuit (15) has a quantization bit number set to about 6, converts the input signal into a digital signal using the first clock signal as a sampling clock, and converts the digital signal into a channel switching switch. Supply to (19).

The vertical synchronization signal included in the Y signal is detected by the vertical synchronization detection circuit (20), and based on the detection signal of the detection circuit (20), the switching pulse generation circuit (21) detects the 6H of the vertical synchronization signal.
A field switching pulse which is inverted at a timing before (H is a horizontal scanning period) is formed.

The switch (19) is switched for each field by the field switching pulse. For example, a digital signal for one field of an odd field is stored in the digital memory (22a), and a digital signal for one field of an even field is stored. It is stored in the digital memory (22b).

Both memories (22a) and (22b) are (6fsc ×
(6 bits) / 60 = 2.15 Mbit capacity.

And the digital signals of the memories (22a) and (22b) are
The analog signals are converted by the D / A conversion circuits (23a) and (23b) and supplied to the 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) The frequency 12fsc second clock signal of the clock generation circuit (18) is divided into 1/3 by the frequency dividing circuit (25) for recording on the tape (1) by each 1/40 second scan. A sampling clock having a frequency of 4fsc, that is, a clock having a frequency 3/2 times the sampling clock is formed.

And the sampling clock of the frequency divider (25) is D /
A conversion circuits (23a) and (23b) are supplied to both conversion circuits (2
3a) and (23b), as shown in FIGS. 4B and 4C, a one-field digital signal written to the memories (22a) and (22b) in 1/60 second is read out in 1/40 second. Is converted to analog.

By this analog conversion, the time axis of the original video signal, audio signal, and the like is expanded by 3/2 times.

The output signals of the conversion circuits (23a) and (23b) are supplied to the recording amplifiers (24a) and (24b) and the rotary transformer (26).
The data is supplied to the heads (3a) and (3b) via the a) and (26b), and is recorded on the tape (1) in the same format as in the standard configuration.

Next, in the reproducing circuit section, reproduced signals of one track of each of the heads (3a) and (3b) shown in waveforms A and B of FIG. 6 are converted into transformers (26a) and (26b), a reproducing amplifier (27a), (27
The signals are supplied to A / D conversion circuits (28a) and (28b) having the same quantization bit number as the conversion circuit (15) in FIG.

Further, in order to form the sampling clocks of the A / D conversion circuits (28a) and (28b) so as to follow the reproduction jitter, the output signal of the reproduction amplifier (27b) is supplied to the band-pass filter (29). 100-fold component of the horizontal scanning frequency f _H in the pilot signal by (29), i.e. single frequency components called frequency f ₄ is extracted.

Furthermore, the output signal of the band-pass filter (29) is
It is supplied to the write clock generating circuit (30) a combination of a circuit and a frequency divider circuit, the clock signal for writing 63/4 times the frequency f ₄ in synchronization with the reproduced signal by the generating circuit (30) (= 4 fsc) Is formed.

Then, the conversion circuits (28a) and (28b) convert the reproduced signal into a digital signal using the clock signal of the clock generation circuit (30) as a sampling clock.

Also, based on the clock signal of the clock generation circuit (30), the digital signals of the conversion circuits (28a) and (28b) are written and accumulated in the digital memories (31a) and (31b).

Further, digital signals of the memories (31a) and (31b) are supplied to a D / A conversion circuit (33) via a field synthesizing switch (32). A signal similar to the output signal of the mixing circuit (8) is formed.

At this time, in order to correct the jitter of the digital signal of one track stored in the memories (31a) and (31b) to return to the original 1/60 second, the reference of the crystal oscillator configuration for controlling the rotation of the cylinder (2) is used. A clock signal for reading the memories (31a) and (31b) is formed using the clock signal of the clock generation circuit (34).

That is, the clock signal of the generating circuit (34) is set to 3/2 times (= 6fsc) of the write clock signal, and based on this clock signal, the digital signals of the memories (31a) and (31b) are read. At this time, as shown in FIGS. 6C and 6D, the digital signal for one track reproduced in 1/40 second is 1/40.
It is read out in 60 seconds and the time axis is compressed to 2/3.

Moreover, since a stable oscillation circuit (34) clock signal is used, fluctuations due to reproduction jitter are compensated for, so-called TB
A C (Time Base Corrector) circuit is formed.

Then, the digital signals read from the memories (31a) and (31b) are synthesized by switching the switch (32) every 1/60 second, and then based on the clock signal of the generation circuit (34), the conversion circuit ( Converted to a continuous analog signal in 33).

Further, the output signal of the conversion circuit (33) is the same as that of the conventional 8 mm type VTR, and the separation circuit (35) having a filter configuration is used.
Are frequency separated.

Then, Y of the demodulation circuit (36), de-emphasis circuit, etc.
The Y signal included in the output signal of the separation circuit (35) is reproduced by the signal processing circuit (37), and included in the output signal of the separation circuit (35) by the frequency conversion circuit (38) and the C signal processing circuit (39). The reproduced C signal is reproduced.

Further, the Y signal and the C signal of the processing circuits (37) and (39) are combined by the mixing circuit (40) to form the same composite video signal as the video signal of the input terminal (4) in FIG. Output to the output terminal (41).

The audio signal included in the output signal of the separation circuit (35) is reproduced by the demodulation circuit (42) and the noise reduction circuit (43), and this audio signal is output to the output terminal (44).

Further, the pilot signal included in the output signal of the separation circuit (35) is reproduced by the pilot reproduction circuit (45), and a signal for tracking control based on the reproduction is output to the output terminal (46).

Then, the output terminals (41), (4
The video signal and the audio signal in 4) are returned to the same time axis as the waveform A in FIG. 4, as shown by the waveform E in FIG.

Therefore, a cylinder (2) with a smaller diameter
With a simple configuration having a small number of heads provided with the plurality of heads (3a) and (3b), recording and reproduction can be performed with the format of the tape (1) being the same as the standard configuration.

Since head switching is less than when four heads are provided and is not different from that in the standard configuration, deterioration of crosstalk characteristics between channels such as rotary transformers (26a) and (26b) due to head switching is suppressed. Thus, deterioration of the image quality characteristics of recording and reproduction is prevented.

Moreover, by controlling the writing and reading of the memories (31a) and (31b) of the reproducing circuit section, the fluctuation based on the reproducing jitter is compensated, and the deterioration of the image quality characteristics is further suppressed.

Since the format of the tape is the same as that of the standard configuration, the recorded tape (1) must be
And can be played back with the standard 8mm VT
You can also play tapes recorded with R.

The cylinder diameter of the cylinder (2), the tape winding angle, and the like are not limited to those in the embodiment.

Further, in the above embodiment, the present invention is applied to an 8 mm VTR, but it is needless to say that the present invention can be applied to various helical scan type VTRs.

〔The invention's effect〕

Since the present invention is configured as described above,
The following effects are obtained.

As in the standard configuration, two heads are provided 180 ° apart from each other in the head cylinder having a smaller diameter than in the standard configuration, and the tape running speed and the cylinder rotation angle are set in the same manner as in the standard configuration.

The time for one scan of each of the two heads at the time of recording and reproduction becomes longer in accordance with the difference in the tape winding angle from that in the standard configuration, but the track angle at rest (the lead angle of the cylinder).
However, unlike the standard time format, the format of the tape is the same as in the standard configuration.

Further, a signal at the time of recording and reproduction is digitally expanded and compressed by a time axis expansion unit of the recording circuit unit and a time axis compression unit of the reproduction circuit unit, and is recorded and reproduced on each track of the tape.

Therefore, it is possible to reduce the size of the cylinder with an inexpensive configuration in which two heads are provided in the cylinder without deteriorating the compatibility of the tape format. Therefore, it is possible to prevent the deterioration of the image quality characteristics of recording and reproduction and to reduce the diameter of the cylinder.

[Brief description of the drawings]

1 shows an embodiment of a video tape recorder according to the present invention. FIG. 1 is an explanatory view of a tape winding angle and a head arrangement. FIGS. 2 (a) and (b) show a standard configuration and a 4-head configuration. Explanatory diagram of the tape winding angle and head arrangement of FIG.
FIG. 4 is a block diagram of the recording circuit unit and a timing chart for explaining the operation, and FIGS. 5 and 6 are a block diagram of the reproducing circuit unit and a timing chart for explaining the operation. (1) Video tape, (2) Head cylinder,
(3a), (3b) ... head, (15), (28a), (28b)
…… A / D conversion circuit, (22a), (22b), (31a), (31
b) Digital memory (23a), (23b), (33)
... D / A conversion circuit.

Claims (1)

(57) [Claims] A helical scan of the tape by a plurality of rotating magnetic heads provided on the cylinder to record and reproduce the video tape, and a wrapping angle of the video tape. 180 °, the cylinder is made smaller than in the standard configuration in which one track of the tape is scanned every half rotation of the cylinder. In this video tape recorder, two rotating magnetic heads having opposite azimuths are attached to the cylinder. Provided at positions 180 ° apart, the tape speed during recording and playback, the cylinder rotation speed are the same as in the standard configuration, and the track angle at rest is different from that in the standard configuration to format the tape. The same signal as in the standard configuration is used, and a recording signal for one track in the standard configuration is applied to the recording magnetic circuit to the two rotating magnetic fields. Time axis extending means for extending the time axis for one scan length of each of the magnetic heads, and a time axis compressing means for digitally compressing and restoring the reproduction signals of the two rotating magnetic heads digitally on the reproduction circuit section. Video tape recorder characterized by the following.