JPH03162702A - Video tape recorder - Google Patents

Abstract

PURPOSE:To reduce the diameter of a head cylinder without increasing the number of heads by providing two rotary magnetic heads having opposite azimuths 180 deg. apart from each other on the head cylinder whose diameter is reduced. CONSTITUTION:The wrap angle of a video tape 1 to a head cylinder 2 (tape wrap angle) is changed from 180 deg. for standard constitution to 270 deg. (3/2 times). The diameter of the cylinder 2 is set to a value (3/2 times) smaller than that for standard constitution, and two rotary magnetic heads 3a and 3b having a positive azimuth and a negative azimuth respectively are provided 180 deg. apart from each other on the cylinder 2. A signal is digitally expanded and compressed by the time base expanding means of a recording circuit part and the time base compressing means of a reproducing circuit part at the time of recording and reproducing, and is recorded and reproduced on each track of the tape. Thus, two heads are provided on the cylinder to miniaturize the cylinder without damaging the compatibility of 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 VTRs such as 8mm VTRs and VHS VTRs, the winding angle of the video tape around the head cylinder (hereinafter referred to as tape winding angle) is set to 180° in the standard configuration. At the same time, two rotating magnetic heads with opposite azimuths, i.e., 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 of video signals is recorded and played back on each track of the tape. be done.

By the way, in order to make VTRs smaller, VHS system V
In TR, VH is smaller than the so-called full case notebook.
S. A VHS compact VTR (hereinafter referred to as a C-type VTR) has been invented which uses a C cassette to reduce the diameter of the cylinder.

This C type VTR is, for example, 19 of the magazine "Television Technology".
As described in the October 1983 issue, pages 54-55 (published by Denshi Gijutsu Publishing Co., Ltd.), the tape winding angle i 2
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 {z 3Q r
It is formed by increasing the speed from pTTl to 45 rpm.

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

At this time, the tape winding angle and cylinder rotational speed of 3 degrees are both 100 times greater than in the standard configuration, so the tape former format is the same as in the standard configuration, and the cylinder can be adjusted without compromising compatibility with the tape former. The diameter can be reduced.

[Problem to be solved by the invention]

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

If an 8-mm type VTR is constructed in the same way as a conventional C-type VTR in order to reduce the diameter of the head cylinder, the same problems as described above will occur.

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

[Means to solve the problem]

In order to achieve the above object, in the VTR of the present invention, two rotating magnetic heads with opposite azimuths are provided at positions 180° apart from each other on a small-diameter head cylinder, so that the tape speed during recording and reproduction can be adjusted. The cylinder rotational speed is made the same as in the standard configuration in which the head cylinder is not made smaller in diameter, the track angle at rest is made different from that in the standard configuration, and the format of the tape is made the same as in the standard configuration, and the recording circuit The section is provided with a time axis extension means for time axis extending the recording signal for each one track in the standard configuration to one scan length of each of the two rotating magnetic heads, and the reproduction circuit section is provided with a time axis extension means for extending the recording signal of each one track in the standard configuration to one scan length of each of the two rotating magnetic heads, and the reproduction circuit section is provided with a time axis extension means for extending the recording signal of one track in the standard configuration to one scan length of each of the two rotating magnetic heads. A time axis compression means is provided for digitally compressing and restoring the time axis.

[Effect]

In the case of the VTR of the present invention configured as described above, two heads of 18001! li [, and the tape running speed and cylinder rotation angle are set in the same way as in the standard configuration.

The time for each scan of both heads during recording and playback becomes 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 format of the tape will be the same as in the standard configuration.

Furthermore, the time axis expansion means of the recording circuit section and the time axis compression means of the reproduction circuit section digitally expand and compress the recording and reproduction signals and record and reproduce them on each track of the tape.

Therefore, it is possible to provide a cylinder with two heads and make the cylinder compact without compromising tape format compatibility.

〔Example〕

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

This embodiment is applied to an 8 mm VTR, and as shown in FIG. 2700 (3
/Hao).

In addition, the diameter of cylinder (2) (cylinder diameter) is set to 278 (2/3 times) smaller than the standard configuration (40 =), and a position 1800 mm apart from this cylinder (2) is set to Similarly, there are two rotating magnetic henodes with positive azimuth and negative azimuth, namely A head (3a) and B head (3a).
3b).

Furthermore, the tape speed and cylinder rotational speed are set to be the same as in the standard configuration, and the track angle (cylinder lead angle) when the tape fl+ is at rest when it is wrapped around the cylinder (2) in the stopped state is set as described later in the standard configuration. The tape format is made the same as the standard configuration.

In other words, in the standard configuration of an 8mm VTR,
As shown in Fig. 2 (a), the video tape (1)' is traveling around the head cylinder (2) by 180', and the tape A (3a) is placed at a position 180' behind the head cylinder (2). , B head (3b)' are provided.

Then, the A head (3a)' and the B head (3b) scan the tape alternately every half rotation of the cylinder (2), and one field (1/60 second) is applied to each track of the tape (0).
Video signals, audio signals, pilot signals, etc. are recorded and played back.

In place of cylinder (2)' in FIG. 2(a), a head cylinder with a diameter 273 times that of cylinder (21') is installed to perform recording and playback without compromising tape format compatibility. It is conceivable to have the same configuration as the C type VTR, as shown in FIG.

In FIG. 2 ('b), 2,700 rolls of video tape [11] are attached to the head cylinder (2) and are running, and the cylinders (2r have A head (3a)', B head (3b)', A Head (3a), B head (3
b) Provided at 900 intervals.

Furthermore, the cylinder diameter, rotational speed, tape speed, and track angle at rest and when running of cylinder (2)' in Figure 2 (a) are set as R, ND, VT and θ0, θ, and Figure 2 ('b)
Cylinder diameter, rotational speed, tape speed, and track angle i R, ND', V when stationary and when running of cylinder f2+
Let T' and θo', , θ represent the tape format compatibility. By increasing the speed t-2 times, 4 heads (3
Each of steps a) to (3b) scans the tape for a period of one field to record and reproduce one field's worth of signals, and the tape format is the same as that shown in FIG. 2(a).

On the other hand, the cylinder diameter, rotational speed, tape speed, and track angle 6 of cylinder (2) when stationary and when running in the case of Fig.
f, ND', vr' and θ0; θt, period scanning is performed as described above, and recording and reproduction of the same track length L (=20π) as in the case of FIG. 2(a) is performed.

At this time, the trace states of heads (3a) and (3b) are set so as to satisfy No. 1, and the track format of the tape is made the same as in the case of Fig. 2 (a) by setting θ = θ to ensure format compatibility. We aim to

Furthermore, as mentioned above, the head (3a),
In order to scan (3b) for 3 times the period of one field (= 1 3 = 1 second) 3 2 60 2 40, the recording circuit section and the reproducing circuit section are constructed using digital memory as shown in Figs. 3 and 5. Configure as shown.

That is, in the recording circuit section, the signal is separated into a luminance signal (Y signal) and a color signal (C signal) in the fourth (5), for example.
The Y signal is input to the modulation circuit (7) via a Y signal processing circuit (6) such as an emphasis circuit.

Then, the Y signal is transmitted to the sync chip 1 by the modulation circuit (7).
k4.2MHz, 100% white level 5.4MHz
The output signal of the modulation circuit (7) is modulated into an FM signal of z, 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 an en7 assist circuit (
The signal is supplied to a low-frequency conversion circuit (lO) via the converter circuit (10), and frequency-converted to a low frequency frequency by this conversion circuit (10), and then supplied to a mixing circuit (8).

Furthermore, the input terminal (one audio signal is connected to the noise reduction circuit 02) on the same time axis as the video signal of the input terminal (4)
) via a modulation circuit (4) with a carrier frequency of 1,5 M}Iz
is supplied to the circuit, is FM modulated by this modulation circuit, and is sent to the mixing circuit (
8).

Then, the mixing circuit (8) modulates the modulation circuit +7+, t
The output signals of 131 and low frequency conversion circuit {10} and the pilot signal for tracking control (ATF) of input terminal 04) are frequency-multiplexed and synthesized, resulting in the same 1 signal as the recording signal of a conventional 8 mm VTR. A signal constituting one field is formed in /60 seconds, and this signal is supplied to the A/D conversion circuit (I5).

On the other hand, the frequency fsc (3.58MH
The color subcarrier signal of z) is detected by the fsc detection circuit 00, and the fsc output signal of this detection circuit 00 is supplied to the first clock generation circuit (17) consisting of a PLL circuit for multiplying by 6, and this generation circuit From the same A/D conversion circuit 05)
, a frequency of 6 fsc (3.58 MHz
x6=21.5MHz) is supplied.

The A/D conversion circuit (l6) has a quantization bit count of 6.
Convert the input signal into a digital signal using the sensory clock signal as a sampling clock, and use this digital signal as a channel switching switch? 19).

Further, the vertical synchronization signal included in the Y signal is detected by the vertical synchronization detection circuit ■■■, and forms a field switching pulse that is detected and rotated by the detection circuit.

This field switching pulse causes the switch (I9) to switch for each field, and 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).

Note that both memories (22a) and (22b) each have (5
The capacity is set to fsc×6 bits)/60=2.15 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, in order to record one field worth of digital signals stored in each of the memories (22a) and (22b) onto the tape fi+ with each 1/40 second scan of the head (Aλ(3b)), the clock generation circuit aS+ The frequency of 12 fsc second clock signal is divided by frequency dividing circuit e25)
The frequency is divided by 1/3 to form a sampling clock with a frequency of 4 fsc, that is, a clock with a frequency 7 times that of the sampling clock.

And the sampling clock of branch circuit 4 is D/A conversion time! (23a) and (23b), and both conversion circuits (23a) and (23b) convert B,
As shown in C, Ma-T-'J (22a), (22
The digital signal of the l field written in 1760 seconds in b) is read out in 1740 seconds and converted into analog.

Through this analog conversion, the time axis of the original video signal, audio signal, etc. is expanded by 372 times.

Then, the output signals of the conversion circuits (23a) and (23b) are sent to the head (3a) via recording amplifiers (24a) and (24b) and rotary transformers (26a) and (26b)
), (3b) and recorded on tape (1) in the same format as in the standard configuration.

Next, in the reproduction circuit section, the reproduction signal of each l track of the head (3a), (3b) shown in waveforms A and B in FIG.
7a) and (27b) to the conversion circuit (15) in Figure 3.
A/D conversion circuit (28a) with the same number of quantization bits as (
28b).

In addition, in order to form the sampling clocks of the A/D conversion circuits (28a) and (28b) by following the reproduction jitter, the output signal of the reproduction amplifier (27b) is supplied to the bandpass filter (29). ) extracts a component 100 times the horizontal scanning frequency fu in the pilot signal, that is, a single frequency component called frequency f4.

Furthermore, the output signal of the bandpass filter is supplied to a write clock generation circuit 1 which is a combination of a PLL circuit and a branch circuit, and this generation circuit generates a write signal at a frequency f4 6374 times (=4fsc) synchronized with the reproduced signal. A clock signal is formed.

Then, conversion circuits (28a) and (28b) convert the reproduced signal into a digital signal using the clock signal of the clock generation circuit 1 as a sampling clock.

Further, based on the clock signal of the clock generation circuit diagram, the digital signals of the conversion circuits (28a) and (28b) are written and stored in the digital memories (31a) and (3tb).Furthermore, the memories (31a), (3lb) digital signal is passed through the field synthesis switch (32'k) to D
A signal similar to the output signal of the mixing circuit (8) in FIG. 4 is formed by analog conversion from the perspective of the converter circuit.

At this time, the digital signal of one track stored in the memories (31a) and (3lb) is corrected for distortion and returned to the original 17
To return to 60 seconds, rotation t of cylinder (2) control-j
A clock signal for reading out the memories (31a) and (3lb) is generated using a clock signal from a reference clock generation circuit (self) having a crystal oscillator configuration.

That is, the clock signal of the generation circuit (self) is set to 372 times (-5fsc) the clock signal for writing, and based on this clock signal, the memory (31a), (3l
The digital signals of b) are read out, and at this time, the digital signals of C and B in FIG.
As shown in D, the digital signal for l tracks played in 1740 seconds is read out in 1760 seconds, and the time axis becomes 2//
It is compressed to 3.

? In addition, since the clock signal of the stable oscillation circuit (own) is used, fluctuations due to playback 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 (3lb) are sent to the switch c! every 1/60 second. After being synthesized by switching z, it is converted into a continuous analog signal by a conversion circuit based on the clock signal of the generation circuit.
Furthermore, the output signal from the conversion circuit is frequency-separated by a separation circuit having a filter structure, as in the case of a conventional 8 mm VTR.

Then, the Y signal contained in the output signal of the separation circuit is regenerated by the output of the Y signal processing circuit such as the demodulation circuit (support) and the de-emphasis circuit, and the frequency conversion circuit ■■■ and the C signal processing circuit (39) C included in the output signal of the separation circuit due to
The signal is played.

Furthermore, the processing circuit (371, (39+ Y signal, C
The signals are synthesized in the mixing circuit HO) and input to the input terminal (
A composite video signal identical to the video signal of 4) is formed and output to the output terminal @1).

Further, the audio signal included in the output signal of the separation circuit (to) is reproduced by the demodulation circuit (42) and the noise reduction circuit (4), and this audio signal is output to the output terminal (44).

Furthermore, the pilot signal included in the output signal of the separation circuit (to) is regenerated by the pilot regeneration circuit 4, and a tracking control signal based on this reproduction is output to the output terminal (f).

Then, due to the time compression described above, the output terminals 11), (
The MJ video signal and audio signal are returned to the same time axis as waveform A in FIG. 4, as shown in waveform E in FIG.

Therefore, by using a simple configuration with a small number of heads, in which two heads (3a) and (3b) are provided on a cylinder (2) with a smaller diameter than before, the format of the tape fi+ can be made the same as the format in the i semi-configuration. Recording and playback are possible.

In addition, head switching is less than when four heads are installed and is the same as in the standard configuration, so deterioration of crosstalk characteristics between channels such as rotary transformers (26a) and (26b) due to head switching is suppressed. This prevents deterioration of image quality characteristics during recording and playback.

Moreover, the memo IJ (31a) of the reproduction circuit section. (3lb
), fluctuations due to reproduction jitter are compensated for and deterioration of image quality characteristics is further suppressed.

In addition, since the tape format is the same as the standard configuration, the recorded tape +11 is
In addition to being able to play back tapes recorded on standard 8mm JVTRs.

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

Further, although the embodiment described above was applied to an 8 mm VTR, it is of course applicable to various VTRs using a helical scan method.

〔Effect of the invention〕

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

As in the standard configuration, two heads are provided 1800 degrees apart from each other in a head cylinder having a smaller diameter than in the standard configuration, and the tape running speed and cylinder rotation angle are set in the same manner as in the standard configuration.

The time for each scan of both heads during recording and playback becomes 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.

Furthermore, the time axis expansion means of the recording circuit section and the time axis compression means of the reproduction circuit section digitally expand and compress the signals during recording and reproduction, and record and reproduce them 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 installed on the cylinder, without compromising tape format compatibility.Moreover, the deterioration of crosstalk characteristics due to hesode switching can be avoided. It is possible to reduce the diameter of the cylinder without causing deterioration, and to prevent deterioration of image quality characteristics during recording and reproduction.

[Brief explanation of the drawing]

The drawings show one embodiment of the video tape recorder of the present invention, and FIG. 1 is an explanatory diagram of the tape winding angle and head arrangement;
Figures 2 (a) and (b) are explanatory diagrams of the tape winding angle and head arrangement in the standard configuration and 4-head configuration, and Figures 3 and 4 are block diagrams of the recording circuit section, for explanation of operation. 5 and 6 are timing charts for explaining the smoke and operation of the reproducing circuit section. (!)...Video tape, (2)...Head cylinder, (3a), (3b) - head, 05). (
28a), (28b) - A/D conversion circuit, (22a),
(22b), (31a). (3lb)--Digital memory, (23a), (23b), (self)...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 set to be larger than 80 degrees, and the tape is helically scanned by a plurality of rotating magnetic heads provided on the cylinder to perform recording and reproduction. In a video tape recorder in which the cylinder is made smaller than the standard configuration for scanning tracks, two rotating magnetic heads with mutually opposite azimuths are installed at positions 180 degrees apart on the cylinder, and the tape speed during recording and playback is adjusted. , the cylinder rotational speed is made the same as in the standard configuration, the track angle at rest is made different from that in the standard configuration, the format of the tape is made the same as in the standard configuration, and the recording circuit section is configured to have the same standard configuration. A time axis extension means is provided for extending the time axis of each one track's worth of recording signals at the time of configuration to one scan length of each of the two rotary magnetic heads, and the reproduction circuit section digitally receives the reproduction signal of each of the two rotary magnetic heads. A video tape recorder characterized by being provided with time axis compression means for compressing and restoring the time axis.