JPH0359801A - Magnetic recording device - Google Patents

Abstract

PURPOSE:To obtain a reproducing signal having desired S/N by comparing the levels of 1st and 2nd recording signals with a desired detection level and controlling gain. CONSTITUTION:The device is constituted of a special reproducing movable head 20, a special reproducing movable head control circuit 29, a level detection control part 50, band pass filters 51-54, detection circuits 55-58, a coefficient control circuit 59, and gain control parts 60-63. The recording levels of the 1st and the 2nd recording signals detected by the level detection means 50 are compared with the desired detection level signal previously set, and the gain of the 1st and the 2nd recording signals recorded on a magnetic tape 5 is controlled 60 in response to the compared result. Thus, the recording signal is recorded on the magnetic tape 5 so that the reproducing signal having the desired S/N may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a magnetic recording device, and more particularly to a magnetic recording device capable of recording two or more recording signals on a magnetic tape at different recording depths.

[Prior Art] Fig. 8 shows a system in which a video signal, an FM audio signal, and a PCM audio signal are recorded over three layers on the same magnetic tape.
1 is a block diagram showing a conventional video tape recorder (hereinafter referred to as VTR) capable of playing back. Also, the 9th
8 is a spectral diagram showing the spectrum of each signal recorded and reproduced by the VTR shown in FIG. 8. These figures are shown, for example, in Japanese Patent Laid-Open No. 63-288402 entitled "Rotating Head Type Multiple Recording/Reproducing Apparatus". Here, - as an example, a video signal and an FM
Audio signals are recorded and reproduced in a manner similar to that of a 5-VH8 VTR. Furthermore, as shown in the 1986 ICASSP lecture manuscript titled "Study on audio signal digitization for video tape recorders," PCM signals of approximately 2.6 Mbps are offset type four-phase differential signals. It is assumed that recording and reproduction are performed using dynamic phase modulation (hereinafter referred to as QDPSK).

Referring to FIG. 8, this VTR includes a video signal recording processing circuit 1, a video signal recording amplifier 2, and a magnetic tape 5 on a rotating drum 3 to record a composite video signal as a video signal processing system circuit. It includes a composite video head 4 for reproduction, a video signal reproduction amplifier 6, a switching circuit 7, and a video signal reproduction processing circuit 8.

On the other hand, in the FM audio signal processing system circuit, an FM audio signal recording processing circuit, an adder circuit 10, an FM audio signal recording amplifier 11, an FM audio signal magnetic head 12, and an FM audio signal reproducing amplification circuit 13 are used. bandpass filters 14a and 14b for separating L channel and R channel signal components of the FM audio signal, respectively;
and an FM audio signal reproduction processing circuit 15 are provided.

On the other hand, the PCM audio signal processing system circuit includes a PCM audio signal recording processing section 16, a PCM audio signal recording amplifier 20, a PCM audio signal magnetic head 21, a PCM audio signal reproducing amplifier 22, and a PCM audio signal reproducing processing section. 23 is provided. The PCM audio signal recording processing section 16 is
/D converter 17 and digital audio signal recording processing circuit 18
and an offset type QDPSK circuit 19. PCM
The audio signal reproduction processing section 23 includes a QDPSK demodulation circuit 24, a digital audio signal reproduction processing circuit 25, and a D/A converter 26.

In addition to the above, this VTR includes a movable magnetic head 27 for special reproduction of video signals, a reproduction amplification circuit 28 for special reproduction video signals, and two movable head control circuits for special reproduction.

Next, the operation of the VTR shown in FIG. 8 will be explained.

The baseband video signal is given to a video signal recording processing circuit 1. In the processing circuit 1, the luminance signal component of the video signal is FM-modulated so that the synchronization tip level is 5°4 MHz and the white peak level is 7.0 MHz. On the other hand, the color signal component is low frequency converted so that the carrier frequency becomes 629 kHz. Through these processes, a luminance signal 30 and a color signal 31 having the spectrum shown in FIG. 9(a) are obtained, which are added together and then supplied to the video signal recording amplifier 2 as an RF video signal. The amplified RF video signal is recorded on a magnetic tape 5 via a rotary transformer (not shown) built into the rotating drum 3 and a composite video head 4.

On the other hand, the RF video signal reproduced by the composite video head 4 is amplified by a video signal reproduction amplifier 6 and then supplied to a video signal reproduction processing circuit 8 via a switching circuit 7.

A baseband video signal is obtained in the processing circuit 8.

The FM audio signal is given to the FM audio signal recording processing circuit 9, and the L channel side is
, 3 MHz carrier waves, and the R channel side are frequency modulated by 1.7 MHz carrier waves, respectively. The spectra of the frequency-modulated L channel FM audio signal 32 and R channel FM audio signal 33 are shown in FIG. 9(C). These FM audio signals 32 and 33 are sent to an adder circuit l.
After being added by O, the amplifier circuit 1 outputs the signal as an FM audio signal.
1 is given. The amplified FM audio signal is recorded on the magnetic tape 5 via a rotary transformer (not shown) built into the rotating drum 3 and the FM audio head 12.

On the other hand, the FM audio signal reproduced by the FM audio head 12 is amplified by the amplifier circuit 13, and then separated into L channel and R channel FM audio signals 32 and 33 by band pass filters 14a and 14b, respectively. Each FM audio signal 32 and 33 is demodulated and subjected to noise low frequency processing in the reproduction processing circuit 15 to obtain an audio signal.

The PCM audio signal is converted into a digital signal by an A/D converter 17 in the PCM audio signal recording processing section 16 . The converted signal is added with an error correction code etc. in the recording processing circuit 18 and then converted into an approximately 2.6 Mbps (7) PCM signal by pulse code modulation. This P
The CM signal is transmitted to the four-phase phase modulation circuit 19 by, for example, 2. QDPSK modulated on a 5MHz carrier wave,
As a result, a QDPSK signal 34 having a spectrum with a bandwidth of ±6.65 MHz centered around 2.5 MHz is obtained as shown in FIG. 9(b). This signal is sent to amplifier 2
After being amplified by 0, the signal is recorded on the magnetic tape 5 via a rotary transformer (not shown) built into the rotating drum 3 and the PCM head 21.

On the other hand, the QDPSK signal 34 reproduced by the PCM head 21 is amplified by the amplifier 22 and then demodulated into a PCM signal by the four-phase phase demodulation circuit 24 in the reproduction processing section 23. The demodulated PCM signal is sent to the reproduction processing circuit 25
The signal is subjected to processing such as error correction, restored to a digital audio signal, and then converted to an analog audio signal by a D/A converter 26.

In addition to the standard recording and playback processing described above, this VT
R is provided with special playback functions such as search playback. In special playback, the tape feeding speed is different from the recording speed (for example, three times), and it is not possible to accurately scan the recorded track using only the composite video head 4 with a fixed magnetic head position. Can not. Therefore, a movable head 27 for special reproduction is provided.

FIG. 10 is a waveform diagram showing the relationship between the trajectory of the head and the envelope of the playback output during fast-forward playback. 10th
In Figure (a), a fixed composite video head 4 is used to
This shows the trajectory of the head when playing at double speed. Since the tape feeding speed is different from the recording speed, the angle between the recording trajectory and the playback trajectory of the head is different, so the 10th
The reproduced output envelope shown in Figure (b) is obtained. On the other hand, when reproduction is performed using the special reproduction movable head 27, the position of the movable head 27 can be displaced by an actuator, so that the trajectory of the head during reproduction can be made to match the trajectory during recording. Therefore, a high quality reproduction output envelope as shown in FIG. 10(d) can be obtained.

As an actuator for driving the movable head 27, an electro-mechanical converter such as a bimorph is used. The RF video signal reproduced by the movable head 27 is amplified by the special reproduction video signal reproduction amplifier 28 and then input to the movable head control circuit 29 . The control circuit 29 controls the actuator of the movable head 27 so that the reproduction output envelope always has a maximum value. By displacing the movable head in a direction perpendicular to the recording track, the actuator can accurately scan the recording track shown in FIG. It turns out. The RF video signal amplified by the amplifier 28 is given to the video signal reproduction processing circuit 8 via the switching circuit 7, where it is restored to a baseband video signal.

Next, the above RF video signal, FM audio signal and QDP
A description will be given of what happens after the SK signal is recorded on the magnetic tape. In the multilayer recording method, in which multiple signals are recorded overlappingly on the same recording track, each signal becomes a noise component due to crosstalk and interferes with each other. Therefore, by changing the azimuth angle of each magnetic head, Efforts are made to reduce interference.

Eighth, in the VTR shown in the figure, three types of signals, RF video signal, FM audio signal, and QDPSK signal, are sequentially recorded on the magnetic tape, so the recording layer has a three-layer structure, and this recording method is Let's call it 3-layer recording.

FIG. 11 is an arrangement diagram showing the arrangement of each head for conventional three-layer recording. In addition, in Table 1, VEP indicates the video head for EP mode, VSP indicates the video head for SP mode, and
MA indicates a head for FM audio signals, and PCM indicates a head for PCM sound PA1 signals. Further, L indicates the L channel, and R indicates the R channel.

FIG. 12 is a head position relationship diagram showing the relationship between the mounting positions of each head. FIGS. 12(a) and 12(b) show the positional relationship between composite video heads 4a and 4b. 12th
As shown in Figure (a), in the composite video head 4a, V
The SP-R head 37a and the vEP-L head 38a are about 740. It is attached at a distance M (corresponding to about 1.4°) of czm.

The same applies to the composite video head 4b.

FIGS. 12(c) and 12(d) show the composite audio head 36a.
and 36b. As shown in FIG. 12(c), in the composite audio head 36a, the L azimuth FM audio head lla and the L azimuth PCM head 19a
and are attached at a distance of about 740 μn. The same applies to the composite audio head 36b.

The specifications, mounting angle, mounting height, etc. of each magnetic head constituting the above composite video heads 4a and 4b and composite audio heads 36a and 36b are shown in Table 1. The arrangement is based on the arrangement of a 5-VHS VTR.

FIG. 13 is a graph for explaining the relationship between the mounting angle and height of the magnetic head and the recording trace recorded on the magnetic tape. In the SP odd mode shown in FIG. 13(a), ○ indicates the VSP-R head 37a, FM audio L head lla and PCML head 19a, and M indicates the mounting angle when converted to 00. FM audio L head 11a
and the head height of the PCML head 19a (therefore, the relative position after recording is shown). In addition, VSP-
The mounting angles of the R head 37a and the ■EP-L head 38a, and the FM audio L head 11a and the PCML head 19a are different by 1.4 degrees, but the differences are omitted for the sake of simplicity.

Note that FIG. 13(b) shows the relationship in EP mode.

FIG. 14 is a sectional view showing a recording cross section of a magnetic tape in which signals are recorded in a superimposed manner on the magnetic tape by three-layer recording. FIGS. 14(a) and 14(b) show recording cross sections in SP odd mode and EP mode, respectively.

As shown in FIGS. 14(a) and 14(b), in the magnetic layer 40 of the magnetic tape 5, each FM audio signal recording layer 41 and a PCM
The audio recording layer 42 and the video signal recording layer 43 are formed in this order from the deep side. Each layer 41 to 43 is formed by sequentially recording each signal from the deep layer side using a head for recording each signal. Therefore, the thickness of the recording layers 41 to 43 in the magnetic layer 40 is not predetermined, but differs as a result due to the difference in recording depth determined by the head gap and recording current of each magnetic head. ing. For example, the PCM signal recording layer 42
The thickness is determined not only by the recording current of the QDPSK signal, but also changes by the recording current of the RF video signal.

FIG. 15 is a schematic diagram illustrating the strength of the magnetic field near the magnetic head. Referring to FIG. 15, P near the magnetic head
Magnetic field (Hx) at point (x,y).

Hy) are obtained by the following equations. The following equation is written in a text entitled "Introduction to Magnetic Recording Technology" (Songgo Denshi Publishing Co., Ltd., June 1988), where g is the length of the head gap. Since the magnetic field in the X direction is important, equation (1) will be considered below. If the recording depth on the magnetic tape is D, then considering that the magnetic field Hx at the depth D is equal to the coercive force Hc of the magnetic tape, and assuming that the magnetic field Hg in the head gap is proportional to the recording current, the following Substitute equation (3) into equation (1).

Therefore, the following equation (4) is obtained from equation (1).

From equation (4), if the recording current length or the gap length g is increased, or the coercive force Hc of the magnetic tape is decreased,
It can be seen that the recording depth D in the magnetic tape can be increased. Note that the magnetic field Hg in the gap of the magnetic head
follows equation (3) if the magnetic head is not saturated, but if it is saturated, the saturation magnetic field in the head gap is given by the following equation (5), where Bs is the saturation magnetic flux density of the magnetic head.

Hg5-Bs/uo-(5) Therefore, the maximum recording depth Ds is expressed as follows from equation (4).

Here, in the case of 5-VHS system, approximately Hc=90
05e, Bs-4000G. Also, tto
-4xlO-' [H/m], [Gco -10
~' [Wb/m 2 co-1 0-'
[H* A/m 2 co.

4πxlO-" [6el-[A/ml, so the following equation is obtained from equation (6).

Ds-1,36g - (7) In the case of S-VHS system, video rad gap gv = 0.4μ
m, the gap gF of the FM audio head is -1.3 μm, so the gap gp of the PCM head =0. 5 μm
is set to The maximum recording depth of each magnetic head at this time is as follows.

Ds (V) −0,54um −= (8a
)Ds(P)=0.68μm −=(8
b) Ds(F)-1,76um-(8c)
Note that since magnetic recording is complicated, the above recording depth is only a rough guide.

On the other hand, the optimal value of recording depth is λ, where λ is the recording wavelength.
/4. RF video signal, QDPSK signal and FM
The center frequency of the audio signal is 6.0MHz and 2.5MHz, respectively.
If MHz and l are 5 MHz, and the relative speed between the magnetic head and the magnetic tape is 5.8 m/s, the optimum value of each recording depth can be obtained from the following equation.

Input 4 (V) = 0, 24 p m −
(9a) 8(P) -0, 58a m -(
9b) entered, (F) −0,97am −= (9c) formula (
8a) to 8c) and formula (9a) to 9C)
Therefore, the following relationship holds true.

Ds (F) Ds (P)=1.08. In other words, the thickness of the recording layer is sufficient for the FM audio signal, but the thickness of at least one of the recording layers must be insufficient for the RF video signal and the QDPSK signal. Making the PCM head gap larger than 0.6 μm will solve the above problems, but QDPSK
This is not practical because it causes problems such as a decrease in head sensitivity to high-frequency components of the signal. Therefore, the V of the three-layer recording system
In TR, the balance between the recording currents of the RF video signal and QDPSK signal is important.

FIG. 16 shows the FM audio signal recording layer 41 when the recording currents for the FM audio signal and the QDPSK signal are fixed and the recording current for the RF video signal is varied. 4 is a schematic diagram showing the relationship between the depths of a PCM signal recording layer 42 and a video signal recording layer 43. FIG. Assuming the optimum current value of the RF video signal as rapt,
Figure 16(a) shows the case of 0.9XIopt.
b) is Iopt, and FIG. 16(c) is 1. IXIo
The cases of pt are shown respectively. In either case,
Although the depth of the FM audio signal recording layer 41 and the recording depth DP of the PCM audio signal recording layer 42 do not change, the recording depth DV of the video signal recording layer 43 increases in accordance with the magnitude of the recording current. Become. Therefore, the thickness D2 of the PCM audio signal recording layer 42 becomes smaller, and the thickness D3 of the video signal recording layer 43 becomes smaller.
becomes larger.

FIG. 17 is a spectrum diagram showing the spectrum of the reproduced signal (an example of EP mode) by the PCM head 19 corresponding to the recording conditions shown in FIGS. 16(a) to 16(c).

In FIG. 17, the color signal is 31.degree. FM audio (L) signal 32.degree.
Spectra of an FM audio (R) signal 33 and a QDPSK signal 34 are shown. The change in the reproduction spectrum due to the RF image signal recording current of 1 V is the largest for the QDPSK signal 34, and Iv is 0.9 Iopt, Iopt, 1.11
It decreases by about 2.5 dB as the value is changed sequentially to opt. In addition, the spectrum shown as IV-0 is QDPS
This is the reproduced spectrum when only the K signal 34 is recorded.

FIG. 18 is a graph showing changes in the PCM block error rate under the recording conditions shown in FIGS. 16(a) to 16(c). As shown in FIG. 18, for each mode of EP and SP, the electric current V is set to 0.91opt,
t, 1. The PCM block error rate worsens by approximately one order of magnitude as the value IIopt is changed sequentially.

Similarly, even when the recording current of the QDPSK signal is changed, the recording depth D of the PCM audio signal recording layer 38
r becomes deeper in accordance with the recording current, the thickness of the FM audio signal recording layer 37 decreases, and the S/N ratio of the FM audio signal deteriorates.

Next, the influence of the characteristics of the magnetic tape 5 will be described. The coercive force Hc of magnetic tape is 850 for S/VHS tape.
However, as shown in equation (4), He is also one of the factors that determines the recording depth. The difference between the 8500 6 e and the 9500 i5 e corresponds to a change in recording current of about 10%, which means that the reproduction signal level of the QDPSK signal 34 changes by about 2 dB.

[Problems to be Solved by the Invention] As mentioned above, in a VTR using a three-layer recording method, the thickness of each recording layer is affected by the magnitude of the recording current forming each recording layer and the coercive force of the magnetic tape. There is a problem in that the S/N ratio of the reproduction signal obtained from each recording layer changes, and as a result, a sufficient S/N ratio cannot be obtained.

The present invention was made to solve the above-mentioned problems, and is intended to provide a magnetic recording device capable of recording two or more recording signals on a magnetic tape at different recording depths.
The object of the present invention is to record a signal on a magnetic tape so as to obtain a reproduced signal having a /N ratio.

[Means for Solving the Problems] A magnetic recording device according to the present invention includes gain controllable amplification means for amplifying first and second recording signals, and amplifying means for amplifying first and second recording signals. recording means for recording the signals on the magnetic tape at equal recording depths; level detection means for detecting the recording levels of the first and second recording signals recorded on the magnetic tape by the recording means; and a means for generating a predetermined desired detection level signal of the second recording signal, a comparison means for comparing the level of the recording signal detected by the level detection means and the desired detection level, and a comparison by the comparison means. and gain control means for controlling the gain in the amplification means in response to the result.

[Operation] In the magnetic recording device of the present invention, the recording levels of the first and second recording signals detected by the level detection means are compared with a predetermined desired detection level signal,
The first record recorded on the magnetic tape in response to the comparison result.
And the gain of the second recording signal is controlled. Therefore, the recording signal can be recorded on the magnetic tape so that a reproduced signal having a desired S/N ratio can be obtained.

[Embodiment of the Invention] FIG. 1 is a block diagram of a recording processing system of a VTR showing an embodiment of the invention. Referring to Figure 1, this VTR
In the video signal processing system, the video signal recording processing circuit 1
, a gain control section 60 for video signals, an amplifier 2 for video signals, and a video head 4. In addition, as an FM audio signal processing system circuit, an FM audio signal recording processing circuit,
Gain control units 61 and 62 for the L channel and R channel of the FM audio signal, an adder circuit 10, an amplifier 11 for the FMM audio signal, and a head 12 for the FMM audio signal are provided. Furthermore, as a PCM audio signal processing circuit, a PC
M audio signal recording processing section 16, gain control section 63 for PCM audio signals, amplifier 20 for PCM audio signals, and PCM audio signal recording processing section 16;
A CM audio signal head 21 is provided. Further, a movable head 27 for special reproduction, a control circuit 29 for controlling the movable head 27, and an amplifier 28 for amplifying No. 13 reproduced by the movable head 27 are provided.

Additionally, this VTR is provided with a level detection control section 50 for controlling the gain coefficients of the gain control sections 60 to 63 in response to a reproduction signal obtained by controlling the special reproduction movable head 27. ing. Level detection control section 5
0 is a band pass filter 51 for separating the FM luminance signal, a band pass filter 52 for separating the FM sound signal 32, a band pass filter 53 for separating the FM sound multiplied signal 33, and QDPSK. A bandpass filter 54 for separating the signal 34, detection circuits 55 to 58 for detecting the level of the signal output from each filter 51 to 54, and gain coefficients of each gain control section 60 to 63 are controlled. 5 coefficient control circuits. A mode designation signal S P/E P, a movable head switching signal MH3W for special reproduction, a video head switching signal VH8W, and an audio head switching signal AH8W are applied to the five coefficient control circuits from another control circuit (not shown).

Next, the operation of the recording processing system of the VTR shown in FIG. 1 will be explained. In addition, video signals, FM audio signals and PC
The basic processing for the M audio signal is the same as that in the conventional VTR shown in FIG. 8, so the explanation will be omitted.

In the VTR shown in FIG. 1, the video signal, FM audio signal, and PCM audio signal are recorded on the magnetic tape 5 via their respective recording signal paths.At the same time as this recording operation, the special playback movable The head 27 is controlled and the recorded signal is reproduced as follows.

FIG. 2 is a layout diagram showing the arrangement of each head applied to the VTR shown in FIG. 1. As shown in FIG. 2, a special playback movable head 27a is attached to the composite video head 4a.
is placed 60° ahead of the composite audio head 36.
A is placed 12 o' ahead. Further, the composite video head 4b, special playback movable head 26b, and composite audio head 36b are arranged in the same manner. The specifications of each head are shown in Table 2 below.By arranging the heads in this manner, as will be explained below, the FM audio signal recording layer 41 and the PCM audio recording layer 42 are and the FM audio signal recording layer 41. Each of the three layer recording states of the PCM audio signal recording layer 42 and the video signal recording layer 43 can be reproduced by the special reproduction movable head 27.

Figures 3 and 4 show SP mode and EP mode, respectively.
FIG. 3 is a schematic diagram showing the locus of each head on the magnetic tape in the case of a mode. First, the operation in the SP mode will be explained with reference to FIGS. 3(a) to 3(d).

At the start of the recording operation, the current of each recording signal is initialized. In the SP mode, an SP mode video (hereinafter referred to as VSP)-R head 37a forms a recording layer on the same track with a 120° delay relative to the FM audio L head 11a and the PCML head 19a. In addition, the FM audio R head 11b and the PCM-R head 1
9b, the VSP-L head 37b similarly forms a recording layer on the same track with a 120° delay.

A special playback movable head 27 is attached at a position 60° ahead of each composite video head 4. When recording is started, the head control circuit 21 moves the movable head 27 to a preset position in response to a mode designation signal SP/EP given from a control circuit (not shown) and a special playback movable head switching signal MH3W. It is moved to the layer recording state monitor position, and the two-layer recording state is reproduced for the L and R channels (FIGS. 3(a) and 3(b)). After that, the two head control circuits displace the special playback movable head 27 to the 3-layer recording state monitor position where the 3-layer recording formed one track ago can be reproduced, and the 3-layer recording state is maintained for the L and R channels. Play.

In this way, by reproducing the two-layer recording state and the three-layer recording state for every two tracks, the recording depth, erasing characteristics, etc. of each recording signal can be constantly monitored during recording. The movable head control circuit 29 is specially movable in the direction perpendicular to the recording track (in the upper direction) so that the reproduction envelope of the QDPSK signal 34 separated by the bandpass filter 54 is maximized during reproduction of the two-layer recording state. Since the head 27 is displaced, a reproduced signal with optimum tracking can always be obtained. Similarly, in the reproduction of the three-layer recording state, the FM signals separated by the filters 51 and 54
The movable head 27 is displaced so that the reproduction envelopes of the IN degree signal 30 and the QDPSK signal 34 are maximized.

In the EP mode, as shown in FIGS. 4(a) to 4d), the video (hereinafter referred to as V
EP)-L head 38a forms a recording layer on the same track two tracks before, and also VEP for FM audio R head 11b and PCM-R head 19b.
- Since the R head 38b also forms a recording layer on the same track two tracks before, the special reproduction movable head 27 reproduces the two-layer recording state and the three-layer recording state for every two tracks, and the recording state is monitored. be done.

FIG. 5 is a spectrum diagram showing the spectrum of each signal reproduced by the special reproduction movable head 27. FIG. 5(a) shows reproduction of a two-layer recording state in SP mode, FIG. 5(b) shows reproduction of a three-layer recording state in SP mode, and FIG. 5(c) shows reproduction of a two-layer recording state in EP mode. FIG. 5(d) shows reproduction of a three-layer recording state in the EP mode. The special reproduction movable head 27 is set at an azimuth angle of ±6°, and the FMM degree signals 30 and L recorded at the same azimuth angle are
For the channel color signal 31, a normal reproduction signal level can be obtained, but since the FM audio signal 32 and the FM sound double signal 33 are recorded at different azimuth angles, they are reproduced as noise components due to crosstalk. Since each of the above signals is recorded in multiple layers on the same track, each reproduced signal level is detected by the level detection control section 50 in order to obtain an appropriate reproduced signal level for each signal. That is, the detection circuit 55 detects the level of the FM luminance signal from the signal applied via the filter 51. The detection circuit 5 detects the signal given through the filter 52.
6, the X level is detected in the FM audio L. A detection circuit 57 detects the level of the FM audio R signal from the signal applied via the filter 53. Filter 54
QDP is detected by the detection circuit 58 from the signal given through the
The level of the SK signal is detected. Detection circuit 55 or 5
The level of each signal detected by 8 is determined by coefficient control circuit 5.
given to 9.

The coefficient control circuit 59 receives a mode designation signal SP/EP, a video head switching signal VHSW, and an audio head switching signal AH3.
W. In response to the special playback movable head switching signal MHSW, it is determined whether the playback signal level in each of the two-layer recording state and the three-layer recording state is appropriate according to the recording mode, as shown in FIGS. 3 and 4. As shown, the judgment is made every four tracks. This determination operation is performed using a look-up table (previously provided in the five coefficient control circuits) that stores a plurality of signal levels.
This is done by referring to the control table) and controlling the gain coefficients of the gain↑;1 control units 60 to 63 so that each reproduced signal level satisfies the set value. As a result, each recording signal level is controlled to a desired desired value.

Through the recording signal processing described above, FM audio signals, PC
Since the M audio signal and the video signal are appropriately gain controlled and recorded on the magnetic tape using the three-layer recording method, the recording depth of each recording layer is set to the most preferable depth, that is, the S of each playback signal in the playback operation. Recording can be performed so that the /N ratio becomes optimal.

FIG. 6 is a flowchart showing the main processing in the above recording operation. The overall recording processing operation will be summarized with reference to this flowchart.

First, when a recording operation is started, the recording current for each recording signal is initialized. (Step 101). Next, the special reproduction movable head 27 reproduces the recording signal recorded on the magnetic tape in the two-layer recording state or the three-layer recording state. (Step 102). Next, the level of each reproduced signal reproduced by the movable head 27 and amplified by the amplifier 28 is detected by the band pass filters 51 to 54 and the detection circuits 55 to 58 (step 103). Next, by referring to the control table 107, it is compared and determined whether the desired reproduction level is obtained for each reproduction signal (step 104).
. Based on the comparison and determination results, the five coefficient control circuits control the gain coefficients of each of the gain control units 60 to 63 (step 105).

Each gain control section 60 to 63 controls the gain of amplification of each recording signal based on the gain coefficient. Each amplified recording signal is recorded on the magnetic tape via each magnetic head (step 106). The recorded tracks on the magnetic tape are played back again by the movable head (step 102) and the above-described operations are repeated.

FIG. 7 is a schematic diagram showing another control locus of the special reproduction movable head of the VTR shown in FIG. 1.

Figure 7(a) shows the case of SP mode, and Figure 7(b)
indicates the case of EP mode. SP shown in Figure 3
In the case of the mode, since the two-layer recording state and the three-layer recording state are reproduced by the movable track 27, each state is detected using two tracks for each track.
By scanning the movable head 27 over two tracks as shown in FIG.
Levels can be detected for the layer recording state and the trilayer recording IA state. Regarding the EP mode, Fig. 7 (b
), the reproduction level of each state can be detected by one scan. These movable heads 27 are controlled in response to control signals output from a control circuit 29.

In the above embodiment, the suitability of each reproduction signal level in the two-layer recording state and the three-layer recording state was judged every four tracks, and each recording signal level was controlled. A system in which the suitability of the playback signal level of both or one of the FM audio signal and the PCM audio signal and, in the case of a three-layer recording state, the determination of the suitability of the reproduction signal level of the video signal and the PCM audio signal or both, and the control of the recording signal level are performed for each two tracks. It may be.

Furthermore, in the above embodiment, a case has been described in which the movable head 27 for special playback is arranged 601 in front of the composite video head 4 and 60 degrees behind the composite audio head 36. The movable head 27 is at least in front of the composite video head 4 and in front of the composite audio head 36.
It suffices if it is placed at a position behind the

Further, in the above embodiment, the magnetic heads are combined, but an It- head may also be used.

Further, in the above embodiment, the special reproduction movable head 27 having an azimuth angle of ±6'' was used to detect each recording signal level, but a movable head for monitoring having another azimuth angle is separately provided. You can.

Further, detection of each signal level in the three-layer recording state may be performed from other tracks recorded before the tracks shown in FIGS. 3 and 4.

Furthermore, in the above embodiment, the recording signal level is detected using FM.
Although this was carried out for the M degree signal 30, FM audio signal 32, FM sound multiplied signal 33, and QDPSK signal 34, it may also be carried out for the L channel color signal 31 for the video signal, and for the FM audio signal The process may be performed for either the audio signal 32 or the FM sound multiplied signal 33.

In addition, control of each recording signal level is performed using the FMfiltration signal 30 and the L channel color signal 30 for the video signal.
For the FMg-voice signal, the L channel and R channel may be controlled separately, but the recording signal level may be controlled simultaneously after adding the two signals.

Further, in the above embodiment, the level of the recording signal was controlled for each signal in the three layers, but the level of the recording signal may be controlled only for a specific signal.

Furthermore, although the signals recorded in the first layer, second layer, and third layer are FM audio signals, PCM audio signals, and video signals in the above embodiments, other signals may be used, and each recording The signal modulation method may be another method.

Furthermore, a movable coil or the like may be used instead of a bimorph as the actuator of the special reproduction movable head 27.

[Effects of the Invention] As described above, according to the present invention, the gain of a recorded signal is controlled in response to the reproduction level of signals recorded at different recording depths, so that a desired S/N ratio can be achieved. A magnetic recording device has been obtained which records a recording signal so that a reproduced signal with n' is obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a recording processing system of a VTR showing an embodiment of the present invention. Figure 2 shows the VT shown in Figure 1.
FIG. 3 is a layout diagram showing the positions of each head applied to R. FIGS. 3 and 4 are schematic diagrams showing the trajectories of each head on the magnetic tape in the SP mode and EP mode, respectively. FIG. 5 is a spectrum diagram showing the spectrum of a signal reproduced by the special reproduction movable head of the VTR shown in FIG. FIG. 6 is a flowchart showing the main recording processing operations of the VTR shown in FIG. 7th
This figure is a schematic diagram showing another control locus of the special reproduction movable head of the VTR shown in FIG. 1. Figure 8 shows the conventional V
It is a block diagram showing TR. FIG. 9 is a spectrum diagram showing the spectrum of the reproduced signal of the VTR shown in FIG. FIG. 10 is a waveform diagram showing the relationship between the trajectory of the head and the envelope of the playback output during fast-forward playback. FIG. 11 is an arrangement diagram showing the arrangement of heads for conventional three-layer recording. FIG. 12 is a head position relationship diagram showing the relationship between the mounting positions of each conventional head. Figure 13 shows
3 is a graph showing the relationship between the attachment state of a magnetic head and a trajectory recorded on a magnetic tape. FIG. 14 is a sectional view showing a cross section of a recording layer of each signal recorded on a magnetic tape by three-layer recording. FIG. 15 is a schematic diagram illustrating the strength of the magnetic field near the magnetic head. FIG. 16 is a schematic diagram illustrating the relationship between the recording depth of each recording signal and the thickness of the recording layer. FIG. 17 is a spectrum diagram showing an example of a reproduced signal spectrum under the recording conditions shown in FIG. 16. Figure 18 shows the PC under the recording conditions shown in Figure 16.
It is a graph showing M block error rate. In the figure, 20 is a movable head for special reproduction, 2 is a special reproduction movable head control circuit, 50 is a level detection control part A1, 51 to 54 are band pass filters, 55 to 5
8 is a detection circuit, 5 is a coefficient control circuit, and 60 to 63 are gain control sections.

Claims (1)

[Claims] At least a first and a second separable in a regeneration process.
A magnetic recording device for recording recording signals on a magnetic tape at different recording depths, the amplifying means capable of controlling the gain of each signal for amplifying the first and second recording signals; recording means for recording first and second recording signals amplified by the amplification means on a magnetic tape at different recording depths; and first and second recording recorded on the magnetic tape by the recording means. Level detection means for detecting a recording level of a signal; means for generating a predetermined desired detection level signal of the first and second recording signals; and a level of the recording signal detected by the level detection means and the desired level. and gain control means for controlling the gain of each signal in the amplification means in response to the comparison result by the comparison means.
Magnetic recording device.