JPS6272286A - Video tape recorder - Google Patents

Abstract

PURPOSE:To realize a high definition VTR with simple constitution by applying time axis correction based on a reproduced tracking pilot signal. CONSTITUTION:The 1st and 2nd band pass filters 16, 17 extract each frequency component, the level is detected by the 1st and 2nd detection circuits 18, 19 and a comparator 20 compares both of them. A tracking error signal is utilized as a phase error signal of a capstan motor driving a tape. A digital TBC 10 applies A/D conversion and write on a memory based on a clock having a time axis fluctuation equal to that of a reproducing signal. That is, a pilot signal recorded for the tracking control is used at the reproduction to apply time axis fluctuation correction of a reproduced MUSE signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of Industrial Application The present invention relates to a video tape recorder (VTR) for recording and reproducing a MULK signal, which has been proposed as a transmission system for high-definition TV signals.

(Example 1) The conventional MULE system uses digital image signal processing technology to compress the band of high-quality TV signals and transmit them.
One image is completed with 4 fields. In addition, in order to perform interpolation operation in units of 4 pixels in the horizontal direction, it is necessary to significantly reduce the residual time axis error compared to V'r'H that corresponds to the conventional NT80 method (for the MULK signal, For example, N1 (K Giken Monthly Report Vol. 27, No. 7, PP
, 19-50) 0 Therefore, a TBO (time axis variation correction device) is essential, but since a positive polarity digital synchronization signal is used in the MULK signal, there is a synchronization signal that can separate the imaging width required for TBO. No 0 For this reason, the MULg signal is time-compressed, negative polarity synchronization and burst signals are added and recorded in the gap, and the TBO
A method has been proposed for use in equipment (Hitachi Hyoron, VO
L, 67, No, 5. P.P.

63-66) 0 し→ Problems to be Solved by the Invention However, in the above method, the circuit configuration for regenerating two sickles becomes complicated. In other words, the M2S requires a new configuration for compressing and expanding the time axis of the signal, and a configuration for creating and adding negative polarity synchronization and burst signals.

(b) Means for solving the problem Therefore, in the present invention, the tracking pilot signal superimposed on the MUSg signal during recording is reproduced to create a clock signal for time axis correction, and the time axis correction is performed. Let's do it.

(E) Since time base correction is performed based on the reproduced tracking pilot signal, a high-quality VTR with a simple device configuration can be realized.

(To) Example An example will be described below according to the drawings.0 Figure 1 is a circuit block diagram of the example, Figure 2 is a circuit block diagram of a synchronous oscillation circuit, Figure 3 is a circuit block diagram of TBO, and Figure 4. FIG. 5 is an explanatory diagram showing the relationship between tracks recorded on a tape and pilot signals, and FIG. 5 is a diagram showing the relationship between pilot signals.

In Figure 1, +1++2+ is a terminal to which a head switching signal is input, (3) is an input terminal for playback output from the preamplifier, (4) is an output terminal for a tracking control signal, and (51) is an input terminal for the playback output from the preamplifier.
(6) is an input terminal for the reproduced MULK signal after demodulation, and (6) is an output terminal for the M08g signal after time axis fluctuation correction.

Further, (7) is a pilot signal generation circuit, (8) is a tracking error signal generation circuit, (9) is a time axis fluctuation correction clock signal generation circuit, and α1 is a TBO.

The pilot signal generation circuit (7) has an oscillation frequency of 16.2
MHz (equivalent to 480F!!, FH is 33w75MHz
is the horizontal frequency of the M08E signal).
1. Frequency dividing circuit (13) Creates and outputs a frequency selection control signal (13a) based on the frequency selection control circuit α3. Frequency division circuit (1z)
13a) substantially controls the frequency division ratio. Then, from the branch circuit (12), four pilot signals Cf1)Cfz)Cfs)(/4) having different frequencies are outputted in a predetermined order. Also, each pilot signal (fl)
The output period of ~(f4) is approximately equal to the period during which one track is scanned by one magnetic head. For example, a 2-head helical arm VTR has a rotation speed of 1800.
r.

pm, then it is 1/6o second.

The frequency of the pilot signals (fl) to (fl) is (f4
) is set to 151KHz (4,5F!:”PIN).In other words, the frequency division ratio of the frequency divider circuit fi3 is changed from 1/16 to 1/16.
Since each pilot signal (fl) to (f4) controlled by 137.1/96.1/107 is set to the above frequency, each pilot signal (fl) to (f4) is controlled by
f4), there is a relationship shown in FIG. Since each pilot signal is selected in relation to the recording track formed on the tape, (at the time of recording, the FM modulated MUsEM signal and the pilot signal from the branch circuit (1B) are superimposed and recorded). Pilot signal (fl) ~ (/
4) is recorded on a tape (TI) as shown in FIG. 4. Tracking control is performed using these above relationships.

This tracking method is similar to the method adopted for 8MVTR, and an IC for 811+1V'I'R can be used.

The tracking error signal generation circuit (8) includes a low-pass filter (1) that separates the reproduced pilot signal from the reproduced signal.
41, this low bass filter (141 output and branch circuit (
1z output (L9, first band pass filter tte, tsFH that passes the α5FH frequency component)
A second band pass filter (171,
It is equipped with the first and second detection circuits (18α9, comparator 2, inverter, and changeover switch).

During playback, the pilot signals (fl
) to (f4) are created and supplied to the mixing circuit U. Then, the reproduced pilot signals from the track being traced by the head (printer) and the adjacent tracks are mixed into the mixing circuit (
Since it is applied to I51, the level of the α5FH frequency component and the level of the tsFH frequency component in the output of the mixing circuit 151 indicate the position of the head relative to the track.

Therefore, the first and second band pass filters α61 (L71
Extract each frequency component and set its level to the first and second
It is detected by the detection circuit m5cas, and the two are compared by the comparator (2). Furthermore, since the polarity of the comparator j output is reversed depending on the track traced by the head (8), the polarity of the tracking error signal is reversed for each track by the inverter 12D and a changeover switch controlled by the head switching signal. 0 This tracking error signal is used as a phase error signal for the capstan motor that drives the tape.

The time axis fluctuation correction clock signal generation circuit (9) includes a sixth and fourth clock signal generating circuit corresponding to each pilot signal (fl) to (f4).
, 5th and 6th band bus filter c2511261I2
71@, the second selection switch side, and a synchronous oscillation circuit ■.

The synchronous oscillation circuit is basically a PLL, as shown in Figure 2.
The circuit includes a phase comparator circuit C11l, a loop filter (
6), Voltage controlled oscillator circuit (VCtO) CR2 each bit o
TS) 5/160 frequency divider circuit corresponding to signals (fl) to (f4), '7137 frequency divider circuit ω, 1796 frequency divider circuit, 1/107 frequency divider circuit (support), each frequency divider circuit A second selection switch side for selecting the output is provided.

The first and second selection switch sides (are frequency selection control signals (
The state is controlled by 15a). During playback, the bandpass filter and frequency divider circuit corresponding to the playback pilot signal (same frequency as the output of the branching circuit α2) obtained from the track traced by the head circle are selected by the first and second selection switches ω. n. A frequency signal of 16.2 MHz is always obtained as the output of the synchronous oscillation circuit (2). Furthermore, since the synchronous oscillation circuit (■) is a PLL circuit, the clock signal for time axis fluctuation correction, which is the oscillation output, is V
0TB containing the same time axis fluctuation as the TFI playback signal
O (time base collector, time axis fluctuation correction device) Qα
is a digital TBO as shown in FIG.

In other words, an A/D that inputs the demodulated signal to M08.
Conversion circuit 11 Digital memo 1 Jitll, D/A conversion conversion circuit Write clock generation circuit that receives the clock signal for time axis fluctuation correction as input Read clock generation circuit that receives the signal from the 16.2 MHz reference crystal oscillator circuit -
A write/read control circuit is provided which controls the operation of the digital memory l by inputting the write and read clocks.

In digital TBCtC1 (j, A/D conversion and writing to memory are performed based on a clock having the same time axis fluctuation as the reproduced signal. Then, based on a signal of t6.2MHz, which is the accurate sampling frequency of the MUSE signal) By reading out the signal and performing D/A conversion, a MULB signal from which time axis fluctuations have been removed can be obtained.

That is, by using the recorded pilot signal during reproduction for tracking control, reproduction M0
Time axis fluctuation correction of the 8E signal is performed.

In FIG. 4, the signal recorded on one track may be the signal for one field, or the signal recorded on one track may be the signal for one field f1.
A signal divided into /n may also be used.

(G1) Effects of the Invention As described above, the present invention uses the pilot signal recorded for tracking to correct time axis fluctuations, so the configuration is simple and the invention is effective.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 are circuit block diagrams of the embodiment,
FIG. 4 is an explanatory diagram showing recording tracks, and FIG. 5 is an explanatory diagram of pilot signals.

Claims (1)

[Claims] (1) a tracking control means that performs tracking control based on a pilot signal superimposed on an information signal; a clock signal generation means for time axis variation correction that generates a clock signal for time axis variation correction based on the pilot signal;
A video tape recorder comprising a time axis fluctuation correction device that corrects time axis fluctuations of a reproduced information signal based on the time axis fluctuation correction clock signal.