JPS5853286A - Magnetic recorder - Google Patents

Abstract

PURPOSE:To realize the accurate compensation of a time axis, by setting the polarity of the reference signal of a horizontal period necessary for compensation of time axis of the chrocminance signal component so that the FM frequency which is modulated by the reference signal is higher than the FM frequency which is modulated by the chrominance signal. CONSTITUTION:A composite color video signal SI which is supplied to a terminal 1 is fed to the 1st LPF3 and the 1st HPF4 to be separated into a low band component SL of the luminance signal and a high band component SH of the chrominance signal. At the same time, the signal SI is supplied to a synchronous separating circuit 5 and a burst gate circuit 7. For a burst signal SB extracted through the circuit 7, the basic wave component is extracted through a frequency divider 8 and an LPF9. Thus the signal SB is turned into the 1st reference signal SBL for compensation of time axis. On the other hand, the horizontal synchronous signal is turned into the 2nd reference signal for compensation of time axis after a delay 16 and a phase delay 17 to be synthesized with the high band component SHC which received a frequency conversion. The polarity of the 2nd reference signal is selected so that the sink chip level exists at the side of the positive polarity basing on the pedestal level.

Description

DETAILED DESCRIPTION OF THE INVENTION Conventional magnetic recording devices generally record a luminance signal and a color signal (carrying color signal) on one magnetic track.

A magnetic recording device to which the present invention can be applied does not adopt such a recording method, but instead stores a luminance signal and a color signal on separate magnetic tracks, and in the case of a composite color video signal, a signal indicating the luminance component ( Each signal is divided into two, a low frequency signal) and a signal indicating color components (high frequency signal).
A magnetic recording device that modulates and records information on separate magnetic tracks.

This invention is suitable for application to such a magnetic recording device, and in particular, the polarity of a horizontal period reference signal used for correcting the time axis included in a high frequency signal can be determined from this reference signal 9. By selecting the modulated FM carrier frequency to be higher than the FM carrier frequency modulated by the signal indicating the color component, it is possible to accurately correct the time axis.

Next, a case in which an example of the present invention is applied to a magnetic recording device employing the above-mentioned special recording method will be described with reference to FIG. 1 and subsequent figures.

FIG. 1 shows a recording device, and FIG. 2 shows its reproducing device. In FIG. 1, terminal (1) is a supply terminal for a composite color video signal 8i (the frequency characteristics of which are shown in FIG. 3A). In cases where the brightness signal and color signal can be obtained separately, such as the output of a television camera, the brightness signal SY is sent to the terminal (2Y), and the color signal Sc is sent to the terminal (2C).
) K is supplied. In the following explanation, the composite color video signal Si will be explained.

The composite color video signal SI supplied to the terminal (1) is the first
The signal is supplied to a low-pass filter (3) and a first bypass filter (4) to divide the signal band into two. 1st
As shown in FIG. 3B, a low-pass filter (3) extracts a low-frequency signal SL containing a signal indicating a luminance component from the composite color video signal SH. The band of this low frequency signal SL does not have to be randomly selected to about 3 MI4z as in the conventional case, but is arbitrary. The example in Figure 3 is basically the same as before (3
MHz K is selected.

On the other hand, in the first bypass filter (4), as shown in FIG. 3C, the high frequency Ig signal SH representing the color component of the composite color video signal Si is extracted. Therefore, this high frequency signal SH includes both a color signal component (carrier color signal) and an island luminance signal component. And the band of this high frequency signal SH is
The cutoff frequency is selected so that the high frequency components of the low frequency signal SL partially overlap. Therefore, the bandwidth WR of the high frequency signal SH divided by the first noibus filter (4) is wider than that of the conventional one.

The composite color video signal SI is further supplied to a synchronization separation circuit F51 to separate composite synchronization pulses COMP and S, of which the horizontal synchronization pulse PH is supplied to a burst flag pulse generator (6) to form a burst flag pulse FB. Then, the burst signal sB is extracted from the composite color video signal S■ supplied to the burst gate circuit (7). This burst signal SB is passed through a step down converter (8) to 1
The frequency is lowered to /2, and the fundamental wave component is extracted by being supplied to a low-pass filter (9). This fundamental wave component burst signal SBL is used as the first burst signal SBL for time axis correction.
It is combined with the low frequency signal sL in a synthesizer Ql) as a reference signal for the signal. In this case, since the horizontal synchronizing pulse PH portion of the low-pass signal SL divided by the low-pass filter (3) is as shown in FIG. 4A, the first reference signal 8
BL is inserted on the back porch side of the horizontal synchronizing pulse PH in the same way as the normal burst signal SB.

Note that the burst signal is set to 1/1 as the first reference signal SBL.
The reason why the frequency is lowered to 2 is when the band of the low frequency signal SL is 3. OM
This is because it is limited to Hz.

A low frequency signal S() into which the first reference signal SBL is inserted.

is pre-emphasized by the pre-emphasis circuit (13), then modulated by the modulator (I3), and this F'
The M modulated output SL-FM is recorded on the tape a41ri by the rotary recording head I-IRL.

On the other hand, the high frequency signal sH including the color signal C is processed by the frequency converter +1
51, the signal is converted to a low frequency band. In this example, 91fH(rH
(horizontal frequency) is selected as the low-frequency conversion frequency, and therefore, in this case, the bandwidth of the high-frequency signal SH can be expanded beyond IMHz.

Synchronizing pulses COMP, S including a second reference signal PHH for time axis correction are inserted into the frequency-converted high-frequency signal SHC as well as the low-frequency signal SL. In this case, the high frequency signal S
Since H contains the burst signal sB (Fig. 4B)
), in this example, the horizontal synchronization pulse P is used as the second reference signal.
H is used. Therefore, the synchronously separated synchronous pulse COMP, 8 is delayed for a certain period of time by the delay element uI, further phase-inverted by the inverter 0η, and then the synthesizer (1
81 and is combined into a high frequency signal SHC. In this case, as shown in FIG. 4B, the second reference signal PHH is inserted at the same position as the horizontal synchronizing pulse of the composite color video signal S. The reason why the phase-inverted horizontal synchronizing pulse pH is used as the second reference signal PHH will be described later.

This high frequency signal SHc with the second reference signal PHI (inserted)
is subjected to pre-emphasis processing in a pre-emphasis circuit, and then subjected to FM modulation in a modulator (21).
The M modulated output 5H-F'M is recorded by the rotary recording head HRH on a recording track different from the above-mentioned low frequency signal recording track.

Signal recording is performed using a high-density recording method, and the recording head HR
The azimuth angles of L and HRH are made different and recorded without guard panning (see Figure 5). The playback device (to) is constructed as shown in FIG.

FM low frequency and high frequency signals SL-FM, SHl'%4 recorded on the first and second tracks TL, 'I'H
are the playback heads (recording head 1-IRL, HRH), respectively.
After being reproduced by HPL and HPHK (which may also be used in combination with HPL and HPHK) and amplified by a reproduction amplifier (not shown),
demodulator C31+, respectively.

It is demodulated at 02. The demodulated low frequency signal SL and high frequency signal SHC are sent to time axis adjustment circuits (4Q+, 5
0), the time axis is corrected.

Next, this time axis adjustment circuit, l! The necessity of 50+ and its circuit configuration will be explained.

FM modulated low and high frequency signals SL-FM.

As shown in Figure 5, each SH-FM is recorded at high density, so as shown in Figure 6, there is some dragging during playback, and the position shifted by L from the normal track is set to the head FIPL. , ■■4PH is assumed to play, compared to normal tracking, the playback head ■■PL
Hai! , the reproducing head l]PH reproduces the low frequency signal SL-PM which is one step later, and the high frequency signal 5jI-FM which is two steps earlier.

Therefore, the low frequency signal SL-FM and the high frequency signal 5H-1! reproduced due to this tracking deviation! A time axis error occurs between 'M. Tape 0 bleeding and playback head HPL
, when the relative velocity of HPH is V, the time axis error Δt between each track is Ql+y2Δtni□■.

Therefore, this time axis error Δt must be corrected.

In addition, as mentioned above, by band-dividing the composite color video signal S■, the luminance signal is divided into a low-frequency signal SL and a high-frequency signal 8.
These signals SI7. Since the SHs pass through separate signal transmission systems, the delay times of the two may be slightly different. Therefore, even when no tracking deviation occurs, it is necessary to adjust the time axes so that the delay times of each channel accurately match.

For this reason, each channel is provided with a time axis adjustment circuit (4[), 150).

The example shown in Figure 2 is a case where the time axis of the high frequency signal SHC is fixed and the time axis of the low frequency signal sL is adjusted, and both CCD (41) and 5υ are used as delay elements. This is the case. (42 is a clock oscillator, (4th floor is a driver, its output is supplied to CCD (4υ), and this clock frequency and a predetermined delay time (for example, IH) determined by the number of bits of CCD (4υ) are given to.

The clock frequency of CCD 5]1 is changed according to the time axis error. Therefore, the first and second reference signals SBL and Ptui, which serve as time base references inserted into the low-frequency and high-frequency signals SL and SH, are detected.

First, the high frequency signal SHC delayed by CCD (4υ)
is a synchronous separation circuit (441K is supplied and the second reference signal P
HH is separated (FIG. 7B), and this second reference signal PH
H is the first mono-multivibrator (4 vibrators are activated,
A first multi-output Ml (C in the same figure) having a pulse width corresponding to, for example, the position of the first cycle of the burst signal sB is formed, and furthermore, this first multi-output Ml generates a second mono-multivibrator 06). operates to form a second multi-output M2 (D in the same figure) having a pulse width Z corresponding to one cycle of the burst signal SB.

This second multi-output M2 causes the first gate circuit (9) to operate, and the signal SB' is extracted from the burst signal sB for one cycle from the predetermined cycle (E in the same figure). This signal SB' is supplied to a first comparison pulse forming circuit to form a first comparison pulse φH corresponding to the zero-crossing point of the signal gB.

The first reference signal SBL is also detected by similar means to form the second comparison pulse φL. Therefore, detailed explanation thereof will be omitted, but 541 is the horizontal synchronizing pulse PH (FIG. 8B).
), the separation circuit 5ω and state are third and fourth mono-multivibrators, from which third and fourth mono-multi-outputs M3°M4 shown in FIG. 8C and D are outputted, respectively. Also,
6η is a second gate circuit, from which one cycle of the signal mj3t (Fig. 8E) constituting the first reference signal SBL is extracted, and a second comparison pulse forming circuit 6 is used for the second comparison. A pulse φL1 (FIG. F) is formed.

When there is no difference in delay time and tracking is correct in both channels, the horizontal sync pulse P
The time WL until the second comparison pulse φL is obtained from QI (FIG. 8F) and the second reference signal P
Time W from HH until the first comparison pulse φH is obtained
H (Figure 7F) is equal. Therefore, by comparing the phases of the first and second comparison pulses φH and φL, it is possible to know the amount of time axis correction on the low frequency signal SL side.

Therefore, these first and second comparison pulses φH2φL
is supplied to the phase comparison circuit 6■, and a variable oscillator (VCO) 521 is controlled by the phase comparison output. ■C0C
The clock output of 52 is connected to CCD6υ via driver Q.
supplied to

Therefore, the delay time of CC'D 511 is controlled according to the phase comparison output, so that the time axis of the high frequency signal SHC that has passed through COD (41) coincides with the time axis of the low frequency signal SL that has passed through KCCD (5υ). The time axis, that is, the delay time, is controlled so that.

The high frequency signal SHC delayed for a certain time by CCD (4υ) is converted to subcarrier frequency 3 in the frequency converter (71).
．． It is reconverted into a signal SR centered at 58M1lz (-227, 5fH).

Therefore, the phase of the synchronously separated second reference signal P)IH is inverted at the - of the inverter and made to have the same polarity as the horizontal synchronizing pulse PH, and is then supplied to the horizontal synchronizing pulse PH. 91 phase locked to PH
A signal of 91 fH is formed, and this 91 fH signal and the 3.58 MHz signal output from the oscillator are supplied to the first frequency converter σ, and the signal is 318.fH higher than 3.53 MHz. A signal of 5 fH is formed, which is further supplied to a second frequency converter σ4 to reconvert the high frequency signal SHC to a frequency centered on the subcarrier frequency of 3.58 MHz.

Note that (7) is a removal circuit for the reference signal PHH of M2, (7)
6) is a counter of IAl.

The frequency-reconverted high-frequency signal SH is supplied to a second bypass filter, and the band is limited as desired. Similarly, the low-pass signal SL whose time axis has been corrected is supplied to the second low-pass filter and subjected to band restriction.

That is, the second low-pass filter @4 has a frequency band characteristic narrower than that of the first low-pass filter (3), as shown by the broken line in FIG. 3B.

In this example, its cutoff frequency fc is 2.7 MHz
has been selected. On the other hand, the band characteristic of the 20th pass filter group is also selected to be narrower than that of the first pass filter (4), and as shown by the broken line in FIG. The off-frequency is chosen equal to the cut-off frequency fo of the second low-pass filter. Therefore, the above-mentioned first bypass filter (4
) is at least the cutoff frequency f. The bandwidth WR is determined so that nearby signals are included.

If the frequency characteristics of the second low-pass filter 4 and the second low-pass filter 101 are selected as described above, the overall frequency characteristics including both will be flat as shown by the solid line in Figure 9. Become.

In addition, as shown in FIG. 2, the second low-pass filter includes a pair of low-pass filters (82A).

(82B) is provided, and a luminance signal S is provided as a human video signal.
4. When using Y (Fig. 10) and color signal SC.
A broadband low-pass filter of about 5 MHz (82
A) is selected. When using the composite color video signal S, a low pass filter (82B) having the above-mentioned frequency characteristics is selected. (c) is the selection switch.

The filtered low frequency signal SLO is supplied to a wave remover (trap circuit) (86) button, and the first reference signal SBL is trapped, after which the low frequency signal SLO and high frequency signal SHO are sent to a combiner g37. ) to reproduce the composite color video signal So.

When the recording and reproducing devices (10) and (3o) are configured in this way, a signal indicating a luminance component and a signal indicating a color component are extracted from the input video signal, and the signals are processed and recorded, and the signals are reproduced. Since these signals are then simply reprocessed and then combined, recording can be performed without any restriction on the bands of the luminance signal and color signal. Therefore, since signal processing can be performed while maintaining a wide band, images of higher quality than before can be reproduced.

That is, as in the conventional method, the luminance signal is modulated by 1M, and the color signal is low-frequency converted and then superimposed on this luminance signal and recorded on one magnetic track (Y/C separation recording using color heterodyne method). Then, the luminance signal is 3. □MHz
To this extent, the band of the color signal is limited to several hundred kHz or less, making it impossible to obtain a high-quality image.

Further, since this recording method is not a conventional Y/C separation method, cross colors naturally do not occur. moreover,
Since the signal indicating the color component is processed and recorded separately from the signal indicating the luminance component, the alternating current bias signal of the signal indicating the color component does not change due to changes in the y4 summer level. There is no deterioration in image quality.

Now, in this invention, the second reference signal PHH inserted into the high frequency signal SH is selected to have a polarity as shown in FIG. 4B. That is, the sync tip level is selected so that the sync tip level is on the positive electrode side based on the pedestal level hp. The reason is as follows.

In other words, if the second reference signal)'f(f) is inserted so that the sync tip level is on the negative side (Fig. 11A), this high-frequency signal sH is output to the pre-emphasis circuit I. As shown in Figure B, undershoot US and overshoot O are pre-emphasized.
It becomes a waveform with 8. Therefore, when this pre-emphasized high-frequency signal SHP is PM-modulated, the straight line Qa in FIG.
If the modulation characteristics are as follows, the pedestal level LP
is the frequency f.

The undershoot US is modulated onto the F'M carrier at frequency f+(fl(f.).

Since the undershoot US falls steeply, the frequency at that part is very high, so this undershoot) T
When a 1"M carrier frequency is modulated with a high frequency component included in the JS waveform, an aliasing component due to a beat component generated between the high frequency component of this modulated signal and the FM carrier during demodulation will be mixed into the demodulated output. Due to this aliasing component, the second
The waveform of the falling portion of the reference signal PH■ becomes dull, which results in jitter.

Since the second reference signal -L'HH is a reference signal for time axis correction, if there is jitter in the reference signal itself, the extra range signal S
The time axes of HC and low frequency signal SL cannot be adjusted accurately.

Further, this second reference signal PITH is transmitted to the frequency converter t.
(Since it is also used as a reference signal for 7υ, the second reference signal PH with jitter is
When PLL (71) is driven with H, the PLL output (output of 91fH) also has jitter, and therefore the frequency reconverted high frequency signal SH also has jitter. As a result, color unevenness occurs on the playback screen.

On the other hand, the second reference signal PHH is set such that the sync tip level is on the positive side of the pedestal level Ll).
If you insert
As shown in Figure 1C, the undershoot US level is smaller than in Figure 1B, so the F modulated by this undershoot US is as shown in Figure 13.
The M carrier frequency f2 is definitely higher than the FM carrier frequency f shown in FIG. Therefore, the falling waveform of the second reference signal I'HH is hardly affected by the beat component generated in this case. Therefore, the demodulated 20th reference signal PHH does not include a jitter component.

As explained above, according to the present invention, the high frequency signal sH
Since the polarity of the second reference signal PHI to be inserted into the FM demodulation is selected as shown in Figure 4B, the M2
Since the influence on the 0 reference signal PHH can be significantly reduced, the time axis can be adjusted correctly. Furthermore, with this configuration, the jitter of the second reference signal PHH can be reduced, so
The jitter of the high frequency signal SH after frequency reconversion is reduced, and the occurrence of color unevenness can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a magnetic recording device according to the present invention, FIG. 2 is a system diagram of its reproducing device, FIG. 3 is a frequency characteristic diagram of a video signal, and FIG. 4 is a configuration diagram of a video signal. Figures 5 and 6 are explanatory diagrams of track patterns, Figures 7 to 13
Each figure is a waveform diagram for explaining the present invention. (10) is a recording device, Seki is a playback device, SL is a low frequency signal,
SH is a high frequency signal, PHH is a second reference signal, and LP is a pedestal level. Figure 8 Figure 7 B4゜ Figure 11 First Figure 12 Figure 13

Claims (1)

[Claims] The signal representing the luminance component is FM modulated and recorded on the first magnetic track, the signal representing the color component is low frequency converted and then FM modulated and recorded on the second magnetic track, and the signal representing the color component is FM modulated and recorded on the second magnetic track. Base 41 of the horizontal period added to the signal indicating the color component
A magnetic recording device whose polarity is selected so that the FM carrier frequency modulated by the reference signal is higher than the FM carrier frequency modulated by the signal representing the color component.