JPS63222360A - Magnetic recording and reproduction device - Google Patents

Abstract

PURPOSE:To eliminate the fluctuation in the output of phase system control signals to be formed in accordance with reproduction pilot signals at the time of reproduction and to prevent the wow and flutter of a capstan by averaging the control signals successively by 4 fields each and outputting these signals. CONSTITUTION:The comparison output S10 from a comparator circuit 14 fluctuates in the 4-field period and is inputted to switch circuits 20-23. A switch control part 29 outputs the control signals S12-S16 to the circuits 20-23 in accordance with heat switching pulses S9 and turns on the circuits successively at every field. The data is thereby replaced in holding circuit 24-27 at the timing of once every 4 fields. The signals S16-S19 sampled and held in the circuit 24-27 in such a manner are added and averaged by an averaging circuit 28, from which the comparison output S11 having no fluctuations is outputted. The fluctuation in the output is thereby eliminated and the wow and flutter of the capstan are prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention sequentially synthesizes four types of pilot signals having different frequencies into a video signal, an FM audio signal, etc., and sequentially switches each field to produce a magnetic tape. The present invention relates to a helical scan type magnetic recording and reproducing apparatus that performs tracking control by extracting each pilot signal during recording and reproduction, and is used in, for example, a video tape recorder.

(Prior Art) Conventionally, this type of video tape recorder (hereinafter simply referred to as VTR)
For example, in an 8mm VTR, as shown in Fig. 3, four types of pilot signals f1 to f4 having different frequencies are sequentially recorded on the magnetic tape, a low frequency conversion color difference signal, an FM audio signal, and an FM luminance signal. Each signal is recorded. Among these, four types of pilot signals f, -
As shown in FIG. 4, f, is recorded while circulating in each trunk of the magnetic tape and being superimposed on the FM luminance signal. The frequencies of these pilot signals f, ~r4 are:
As shown in FIG. 5, 6.5 fn, ? ,5 f,I
.

10.5 fH, 9,5rH (fH: horizontal synchronous frequency)
The difference in frequency between the pilot signal of one truck and the pilot signals of adjacent trucks on both sides is fH(16kllz), 3 fH(4
8kllz) nittail.

FIG. 7 shows an example of a block diagram of a conventional VTR that performs tracking control using such pilot signals. Moreover, FIG. 8 shows signal waveforms of each part of the same block diagram.

Hereinafter, tracking control in the normal playback mode of a conventional VTR will be explained with reference to FIGS. 7 and 8.

Four types of pilot signals f, -f4, etc., as described above, are recorded on the magnetic tape a. The reproduced biloft signals reproduced from the magnetic tape a by the rotating magnetic heads b and c are each amplified by a head amplifier d, and supplied to a mixer f via a low-pass filter (LPF) e. On the other hand, the reference pilot signals of frequencies f1 to f4 outputted from the reference pilot signal generation circuit g are sequentially switched by a select circuit, supplied to a mixer r, and mixed with the respective reproduced biloft signals f, to f4. The output of this mixer f is passed through the first band pass filter (BPF)
i and a second band pass filter (BPF) j, where the beat signals S2 and Si (see FIG. 8(C), (dl)) are respectively extracted and supplied to the next stage switching circuit k. These two beat signals S
2. As shown in FIG. 6, Si is a rotating magnetic head b (
or C) the pilot signal f recorded on the video track on which C) is traveling.

and each pilot signal f4 . recorded in the adjacent video tracks on both sides of that video track. f
, that is, the signal has a frequency of fH+3fH. Furthermore, since the polarity of the phase lead/lag of these two beat signals Sz and Ss is opposite for each field, the head switching pulse (H, SW, P) S l
(By performing switching control on the switching circuit according to FIG. 8 (see al), two types of error signals Ss, Ss
(See Figure 8 +1111. (f))] is output to each detection circuit 19m, where it is detected as signals Sh and St with waveforms shown in Figure 8 (g) and (tl), and then the comparator circuit n
is supplied to

In this way, two beat signals S2. Si is a frequency difference signal between the pilot signal recorded on the video trunk on which the rotating magnetic heads b and c run and each pilot signal recorded on the adjacent video tracks on both sides of the video track. If the output levels of both beat signals are equal, it means that the rotating magnetic heads b and c are tracing the video track correctly, and if they are not equal, it means that they are not tracing the video track correctly. therefore,
Both error signals S4 . . . are obtained by switching the polarities of both beat signals S, . The level of Ss is compared by a comparator circuit n, and the comparison output Sa (see FIG. 8 ill) is supplied to a servo circuit (not shown) to perform tracking control.

(Problems to be Solved by the Invention) However, the above-mentioned VTR playback system is
dBloct, and each reproduced pilot signal f, -f4 has a frequency characteristic of dBloct, and even if there is no tracking deviation,
A level difference occurs as shown in FIG. When a phase system control signal is created from each reproduced pilot signal f, -f4 that causes such a level difference, a fluctuation of four field cycles (15Hz) is caused in the comparison output S8, as shown in FIG. There was a problem in that this directly appeared as wow and flutter in the 1511z capstan.

(Means for Solving the Problems) The magnetic recording and reproducing apparatus of the present invention sequentially synthesizes four types of pilot signals having specific frequencies into a video signal, FM audio signal, etc., and sequentially switches each field to generate a magnetic signal. In a helical scan type magnetic recording and reproducing apparatus that records on a tape and performs tracking control using each of the pilot signals during playback, during playback, four phase system control signals are sequentially created based on the respective playback pilot signals.
An output means for averaging and outputting the average field by field is provided.

(Function) The output means sequentially averages and outputs the phase system control signal for each four fields. This eliminates field-by-field fluctuations in the phase system control signal during reproduction caused by level differences between the reproduction pilot signals due to the electromagnetic conversion characteristics of the reproduction system.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic block diagram of a reproducing system of a magnetic recording/reproducing apparatus according to the present invention.

In the figure, l represents four types of biloft signals f.

〜F4 etc. are recorded on the magnetic tape, 2 and 3 are rotating magnetic heads, 4 is a head amplifier, 5 is a low pass filter (LP
F), 6 is a mixer, 7 is a reference biloft signal generation circuit, 8 is a select circuit, 9 is a first band pass filter (1st BPF), 10 is a second band pass filter (28th PPF)
F), 111! In the tillJtA circuit, 12 is a first detection circuit, 13 is a second detection circuit, and 14 is a comparison circuit. These components are the same as those in the conventional circuit described above, so detailed description thereof will be omitted here.

The device of the present invention further includes, in addition to this conventional circuit, a first switch circuit 20, a second switch circuit 21, a third switch circuit 22, and a fourth switch circuit 2 connected to the comparison circuit 14.
3, and a first hold circuit 24 that samples and holds the output from the first switch circuit 20, and a second switch circuit 2.
A second hold circuit 25 samples and holds the output from the third switch circuit 22, a third hold circuit 26 samples and holds the output from the third switch circuit 22, and a fourth switch circuit 23.
4th hold circuit 2 that samples and holds the output from
7. An averaging circuit 28 that adds and averages the data sampled and held in each of these hold circuits 24 to 27.
, a switch control section 29 is added for controlling the switching timing of each of the switch circuits 20 to 23.

That is, as shown in FIG. 2, the comparison output S from the comparison circuit 14. [See figure (b)] is 4 as described above.
It fluctuates with the field period. This comparison output StO is input to each switch circuit 20-23. The switch control unit 29 outputs control signals 81□ to SIS to the respective switch circuits 20 to 23 based on the head switching pulse S9 (see the same figure (al)) [see the same figure (C1 to (f))], ■ for each field. Each of the switch circuits 20 to 23 is sequentially turned on.As a result, each of the hold circuits 24 to 27 is turned on.
In this case, data is exchanged once every four fields. Each signal S16 sampled and held in each hold circuit 24 to 27 in this way
-S19 [see (g) to ('') in the same figure] is the averaging circuit 2.
8 is added and averaged to produce a comparison output S++ with no fluctuation.
(See figure (k))] is output to the next stage servo circuit (not shown). - Note that sequential sampling every 4 fields is
This is to increase response speed. In addition, by sequentially holding samples and averaging them, output fluctuations for each sampling are smoothed out, thereby preventing unnecessary disturbances from entering the capstan control signal.

(Effects of the Invention) As explained above, according to the magnetic recording and reproducing apparatus of the present invention, by sequentially averaging the phase system control signal in units of four fields, it is possible to eliminate output fluctuations of the phase system control signal. It is also possible to prevent capstan wow and flutter caused by this output fluctuation.

[Brief explanation of drawings]

Figure 1 is a schematic block diagram of the reproduction system of the magnetic recording and reproduction apparatus of the present invention, Figure 2 is a signal waveform diagram of each part of the block diagram shown in Figure 1, and Figure 3 is the frequency of the signal recorded on the magnetic tape. Fig. 4 is a diagram showing the recording pattern of each pilot signal on each track of the magnetic tape, Fig. 5 is a diagram showing the frequency spectrum of each pilot signal, and Fig. 6 is a diagram showing how the head traces the track. FIG. 7 is a schematic block diagram of a reproduction system of a conventional magnetic recording and reproduction apparatus, FIG. 8 is a signal waveform diagram of each part of the same block diagram, and FIG. 9 is a diagram showing the output level of each reproduction pilot signal. 1...Magnetic tape 2, 3...Rotating magnetic head 4...Head amplifier 5...Low pass filter 6...Mixer 7...Reference pilot signal generation circuit 8...Select circuit 9...・First bandpass filter 10...Second bandpass filter 11...Switching circuit 12...First detection circuit 13...Second detection circuit 14...Comparison circuit 20
...First switch circuit 2■...Second switch circuit 22...Third switch circuit 23...Fourth switch circuit 24...First hold circuit 25...Second hold circuit 26. ...Third hold circuit 27...Fourth
Hold circuit 28... Averaging circuit 29... Switch control section 82 Figure (a) 59 Ck) 5n 33 Figure 11E5 Figure 6 b (c)

Claims (1)

[Claims] 1) Four types of pilot signals having different frequencies are sequentially synthesized into a video signal, FM audio signal, etc., and are sequentially switched for each field and recorded on a magnetic tape,
In a helical scan type magnetic recording and reproducing device that performs tracking control using each of the pilot signals during reproduction, during reproduction, phase system control signals created based on each of the reproduction pilot signals are sequentially averaged and output in units of four fields. A magnetic recording/reproducing device characterized by being provided with an output means.