JPS6134758A - Rotary magnetic head of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the S/N and the detection sensitivity of a pilot signal as tracking information by forming not only a main magnetic path of a gap on surfaces facing each other of two cores but also similar auxiliary magnetic paths on both sides in the lengthwise direction of the gap with respect to the structure of a rotary magnetic head. CONSTITUTION:The width of a core 1 is made wider than a track width T1 of a video head and is set to T'1 to form faces a1 and a2 in the lengthwise direction of a gap 3, and a magnetic path is formed between side faces b1 and b2 of a core 22. Thus, the quantity of side reading of pilot signals recorded on adjacent tracks is increased to improve the S/N of pilot signals as tracking information, and a high servo loop gain is obtained to improve the tracking control capacity.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a rotating magnetic henode of a magnetic recording/reproducing device.
In particular, the present invention relates to a rotating magnetic head of a magnetic recording/reproducing apparatus that records a pilot signal on a magnetic track and detects the pilot signal during reproduction to perform tracking control.

[Background of the invention]

In conventional household magnetic recording and reproducing devices, such as VTRs, two rotating heads with different azimuth angles are alternately scanned obliquely to the longitudinal direction of a magnetic tape to record video signals without providing a guard band. The so-called rotating head, helical scan, and azimuth recording methods are adopted. Then, tracking control is performed so that the rotary head correctly scans the azimuthally recorded tracks on the magnetic tape during reproduction.

One tracking control method involves recording a pilot signal, which serves as tracking information during playback, on a video track of a magnetic tape by superimposing it on a video signal using a rotating head, and detecting the pilot signal of an adjacent track during playback. A method (A TF control method) has been devised in which a tracking error signal is formed and tracking control is performed.

ATF (Auto-door αt) using Konohiroto signal
i c Trac'h Pinding )) control method can always detect tracking errors,
Since tracking control can be easily automated, there is no need for the user to make tracking adjustments by looking at the reproduced image. Furthermore, it has the advantage that sufficient tracking control performance can be obtained, especially when recording for a long time by narrowing the recording track pitch.

By the way, in this method, since the tracking error is detected from the reproduction level of the pilot signal of the adjacent track, the amount of change in the reproduction level of the pilot signal of the adjacent track with respect to the tracking deviation of the rotary head becomes the tracking error detection sensitivity. Also, the s/ of this regenerated pilot signal is
y greatly affects tracking control performance.

This ATF control method will be explained in more detail below with reference to FIGS. 1 and 2.

FIG. 1 is a magnetization pattern diagram showing an example of a track pattern of a magnetic tape 4 in which a four-frequency pilot signal is recorded superimposed on a video signal.

In FIG. 1, A+ and A2 are video tracks recorded by the rotary video head 5, and B1 and B2 are video tracks recorded by the rotary video head 6.

Further, 11 to f4 indicate frequencies of pilot signals recorded on each video track.

That is, the four-frequency pilot signals 11 to f4 are recorded alternately at a predetermined p-tem for each video track, as shown in the figure.

The frequencies 11 to f4 of these pilot signals are selected to be lower than the frequency band of the video signal and so low that they are not affected much by the azimuth angles of the video heads 5 and 6.

Therefore, when the video heads 5 and 6 scan the recorded video track during playback, not only the pilot signal of the main video track that is being correctly scanned, but also the pilot signals from the video tracks adjacent on both sides of the main video track are detected. be able to.

Therefore, as will be described later, by detecting the reproduction levels of the pilot signals from both adjacent tracks and determining the level difference, it is possible to obtain an accurate tracking error signal that includes the direction and magnitude of the tracking deviation. .

Now, the frequency of the four-frequency pilot signal shown in Fig. 1 is ・-'+ = 6JfH# f2='5fm y f
If s = 10.5fa + fa -9-5fH (here, fH is the frequency of the horizontal synchronization signal of the video signal),
When scanning video track A11A2, if the tracking shifts to the right, lf+ -fll-1f--f
41 = If the fm component increases and shifts to the left, If,
-f,l -lfi -f21=3fH component increases.

In addition, when scanning video tracks B, E2, 1
When tracking shifts to the right, 1f2-f, 1=I
fa flll = 3 If the fH component increases and shifts to the left, lf2'-f+l = lf4- f, l = tH
FIG. 2 is a block diagram mainly showing an example of a tracking error signal forming circuit that forms a tracking error signal from a reproduced pilot signal.

In the figure, reference numeral 7 denotes a video head 5. A local signal P having the same frequency as the pilot signal recorded on the main video track that the video head 5 or 6 is about to scan is generated in accordance with the head phase detection signal SW of one frame period that detects the rotational phase of the video head 5 or 6. This is a local signal generation circuit that generates.

-9 is the regenerated pilot signal PL supplied from terminal 8.
10 is a frequency conversion circuit, 11.12 is a hand pass filter, 13.14 is an envelope detection circuit, 15 is a differential amplifier, 16.17 is a gate circuit, 18 is an inverter circuit. Note that the circuits 9 to 18 described above constitute the tracking error signal forming circuit 19.

20 is a four-pass filter, and 21 is an output terminal.

In FIG. 2, the regenerated pilot signal p I+' after amplifying the regenerated pilot signal PL inputted from the terminal 8 with the amplifier 9 is converted to the local signal F By mixing with the fH acid component, a signal having the difference frequency between these two signals, that is, the fH acid component and 5 fH acid component composite signal is obtained.

Next, this composite signal is filtered through bandpass filters 11.12
The fH acid component is separated into 3 fm components. Then, the fu acid component 3fH component becomes voltage signals V 1 and 7B having values corresponding to their respective amplitudes by the envelope detection circuit 15.14. Then, the two voltage signals v1. v.

is supplied to the differential amplifier 15.

The differential amplifier 15 calculates the difference between the voltage signals V, , V, and outputs the fH acid component 5fma as the differential output.
Difference voltage signal D+=K(V+Vs), D, w
Obtain K (V, -v, ), (where K is a constant).

The differential voltage signals DI and DB represent the level difference between pilot signals detected from adjacent tracks on both sides of the main track to be scanned.

By the way, in this way, the differential amplifier 15 generates two differential voltage signals IJ1. The reason why Ds is obtained is as follows.

That is, when the main track is A1 or A2, and when the main track is B1
Or, in the case of B2, as described above, the directions of increase and decrease of the fH acid component and the 3fH component with respect to the direction of tracking deviation are opposite, but despite this, the output of the tracking error detection circuit 19 is continuous. This is to obtain a tracking error signal.

Specifically, the output difference voltage signal DI from the differential amplifier 15
, DI and a gate circuit 16.1 provided correspondingly.
Supply to 7. In the gate circuit 16.17, the terminal 23
The head phase detection signal SW supplied from the head phase detection signal SW and a signal whose polarity is reversed by the inverter circuit 18 are used as respective gate signals. , to open the gate.

As a result, the tracking error detection circuit 19 alternately sends signals A, D, and D for each field. Therefore, the tracking error detection circuit 19 outputs 1
Despite the discrepancy between the increasing and decreasing directions of the fH acid component and the 3fH component with respect to the direction of tracking deviation for each track scan, a continuous and accurate tracking error signal can be obtained.

In this way, the tracking error detection circuit 1
The tracking error signal - obtained in step 9 is supplied to the sea-pass filter 20, where it is smoothed into a DC voltage to become the tracking error signal m,/, which is output from the terminal 21◇ After that, the error signal -' is is sent to the motor drive amplifier. Thereby, the rotational speed and rotational phase of the capstan motor are controlled so that accurate tracking is performed during playback.

As explained above, in the ATIF control type magnetic recording/reproducing apparatus, the pilot signal reproduction level (side-leading amount) from an adjacent track of a pilot signal recorded on a video track is used as tracking information. Therefore, as described above, in order to improve the tracking control performance, it is necessary to increase the 87M and (detection sensitivity) of the reproduced pilot signal from the adjacent track.

FIG. 3 is a perspective view showing an example of a conventional video head, and FIG. 4 is a partial plan view showing the main parts of the sliding surface.

In these figures, 1.22 is the core, 2 is the coil, and 3
shows an extremely thin slit-shaped gap formed on the opposing surfaces of the two cores 1 and 22 bonded together.

Furthermore, FIG. 5 shows the bed position and pilot signal reproduction obtained when a pilot signal is recorded using a video head having a structure as shown in FIGS. 3 and 4 and then reproduced using the same head. FIG. 3 is a characteristic diagram showing the relationship with level.

In the figure, Ll is the gap part of the sliding surface of the video head, that is, the signal recording/reproducing part of the video head (hereinafter referred to as
(simply referred to as a video head), T is the track pitch width. Note that the dashed dotted line at the center of the track pitch width T coincides with the center position of the video track 0AASOAB.

As mentioned above, in the ATIF control method, the amount of side-leading of the pilot signal of the adjacent track is detected during playback to form a tracking error signal.
In FIG. 5, the side-leading amount of this PiP7) signal is determined by the reproduction level S1 of the pilot signal from the adjacent track OAA when the video head JL1 is located at the center of the video track OAB, and the noise level (in the non-recording state). (tape playback level) N1 is expressed as the difference t1.

Therefore, when a conventional video head is used, the amount of side reading is very small, which deteriorates the S/N ratio of the pilot signal as tracking information, resulting in a significant deterioration of tracking control performance. .

Furthermore, the slope of the tangent line 01 at the intersection of the pilot signal reproduction level characteristic curve in FIG. 5 and the single point @ line indicating the center of the video track ChB indirectly represents the tracking error detection sensitivity, although this slope is also relatively small. Therefore, there was also a drawback that sufficient loop gain could not be obtained.

These drawbacks are particularly noticeable when recording and playing back tapes with guard bands, where the head width is smaller than the track pitch width; in extreme cases,
In some cases, tracking control became completely impossible.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, and to
To provide a rotating magnetic head for a magnetic recording/reproducing device that can improve the S/N of a pilot signal as tracking information in a TF control system, increase detection sensitivity, and improve tracking control performance as a result. be.

[Summary of the invention]

A feature of the present invention is that a rotating magnetic head is formed on the opposing surfaces of the two cores on both sides of the gap in the longitudinal direction in addition to the main magnetic path of the gap formed on the opposing surfaces of the two cores. The structure is such that a similar sub-magnetic path can be formed.

[Embodiments of the invention]

The present invention will be described below with reference to the drawings, taking a video head as an example, similar to the conventional example.

FIG. 6 shows a video as a rotating magnetic head of the present invention.
FIG. 3 is a partial plan view showing a main part of the sliding surface of an embodiment of the RAD.

In this figure, the same reference numerals as in FIGS. 3 and 4 indicate the same or equivalent parts.

As is clear from FIG. 6, in the video head of this embodiment, the width of the core 1 is extended to a width T11 with respect to the track width T1 of the video head, so that the width coincides with the longitudinal direction of the gap 3. The core 22 is formed by forming surfaces α1 and α2.
side 61. A magnetic path was formed between the two and b2.

That is, in this embodiment, the peripheral part of the gap 6 formed on the opposing surfaces of two cores 1 and 22, the surface α1 of the core 1, the side surface b1 of the core 22, and the surface α2 of the core 1.
A sub-magnetic path is formed between the core 22 and the side surface b2 of the core 22, and the video head is structured such that the amount of side reading of the pilot signal recorded on the adjacent track is increased.

Figure 7 shows the experimentally obtained head position and pilot signal playback level when a pilot signal was recorded using a video head having the structure shown in Figure 6 and then played back using the same head. FIG.

In the same figure, 42 is the gap portion of the video slider sliding surface of this embodiment, that is, the signal recording/reproducing portion of the video head (hereinafter simply referred to as the video head), and T is the track pitch width (same as in FIG. 5). show. It should be noted that the dashed dotted line at the center of the track pitch width T coincides with the center position of each video track OAA, OAB, similarly to FIG. 5.

When a pilot signal is recorded and reproduced using the video head of this embodiment, as is clear from FIG. Since the reproduction level of the pilot signal becomes level S2, the noise level N
The l trv difference (side reading amount) is t2.

This is much larger than the side-leading amount t1 when recording and reproducing using a conventional video head, so the S of the pilot signal as tracking information is significantly increased.
/N is significantly improved.

Furthermore, when the video head of this embodiment is used, the slope of the tangent sO2 at the intersection of the pilot signal reproduction level characteristic curve shown in FIG. , conventional similar mso
, which is significantly larger than the slope of .

Therefore, according to the video head of this embodiment, a sufficiently large servo loop gain can be obtained compared to the case where a conventional video head is used.

That is, it will be understood that when a pilot signal is recorded and reproduced using the video head of this embodiment, the tracking control performance in the ATF control system can be significantly improved.

FIG. 8 is a partial plan view showing the main part of the sliding surface of another embodiment of the video head as a rotating magnetic head of the present invention.

In this figure, the same reference numerals as in FIG. 6 indicate the same or equivalent parts.

The video head shown in Fig. 8 has core 1 and core 2 of the same width.
2 and 2 were attached to each other while being shifted from each other, and a gap 3 was formed at the bonded surfaces.

Therefore, in this video head, the surface a3 of the core 1 and the side surface b5 of the core 22 coincide with the longitudinal direction of the gap 3.
and the surface b4 of the core 22 that coincides with the longitudinal direction of the gap 3.
A sub-magnetic path similar to that of the head shown in FIG. 6 is formed between the magnetic head and the side surface a4 of the core 1.

Therefore, in the video head of this second embodiment, as in the video head of FIG. 6, the amount of side reading of the pilot signal recorded on the radial track increases, and the head as shown in FIG. Pilot signal regeneration level characteristics with respect to position were obtained.

Therefore, even when a pilot signal is recorded and reproduced using the video head of this second embodiment, the s/H of the pilot signal as tracking information can be greatly improved compared to the conventional video head, and Since a large servo loop gain can be obtained, tracking control performance in the ATF control system can be significantly improved.

Further, FIG. 9 is a partial plan view showing a main part of a sliding surface of a third embodiment of a video head as a rotating magnetic head of the present invention.

In this figure, the same reference numerals as in FIGS. 6 and 8 indicate the same or equivalent parts.

The video head shown in FIG. 9 is formed by bonding together two cores, each of which has curved cross-sections as shown in the figure on both side surfaces in the vicinity of the surface where the gap 3 is formed.

For this reason, in this video head, the curved surface α of core 1 is
6 and the curved surface b5 of the core 22, and the curved surface α of the core 1
6 and the curved surface b6 of the core 22, an auxiliary magnetic path similar to the head shown in FIGS. 6 and 8 is formed.

Therefore, even in the video head of this third embodiment, the pilot signal reproduction level characteristics with respect to the head position as shown in FIG. 7 can be obtained, and the S/N of the pilot signal as tracking information is greatly improved. and a sufficiently large servo loop gain can be obtained, so A
Tracking control performance in the T7 control system can be greatly improved.

Incidentally, in the above explanation, the video head of a VTR which records and reproduces a video signal and a pilot signal in a superimposed manner is taken as an example.

However, the rotating magnetic head of the present invention is not limited to only a video head, but is also a rotating head type magnetic recording and reproducing device that performs ATF control by superimposing recording of an audio signal (particularly a POM audio signal) and a pilot signal. The same effect as described above can be obtained even if it is used in

〔Effect of the invention〕

As is clear from the above description, according to the present invention, AT
In a magnetic recording/reproducing apparatus using the F control method, since it is possible to increase the side-leading amount of the reproduced pilot signal, it is possible to improve the S/N of the pilot signal and also increase the detection sensitivity.

As a result, according to the present invention, tracking control performance can be significantly improved.

In addition, VTRs have two modes: a mode in which recording and playback is performed at a normal standard speed (hereinafter referred to as SP mode), and a mode in which the tape speed is lower than the standard speed and recording and playback is performed for a long time by narrowing the recording track pitch (hereinafter referred to as SP mode). There is an ATF control system that shares the LP mode.

In this type of VTR, the track pitch in SP mode is longer than in LP mode and has a wider guard band, making it difficult to obtain a sufficient amount of side reading. Therefore, in the past, the video head was switched for each SP mode.

However, if the video head of the present invention is employed, as described above, a sufficient side-leading amount of the pilot signal can be obtained, so that good tracking control performance can be obtained with the same head in both modes.

Therefore, according to the present invention, an AT of a type that can share both sp/:t and p modes. The structure of the control system VTR can be simplified and the cost can be reduced as well.

[Brief explanation of the drawing]

Figure 1 is a magnetization pattern diagram showing an example of a track pattern of a magnetic tape in which a four-frequency pilot signal is recorded superimposed on a video signal. Figure 2 shows a tracking error signal formed mainly from the reproduced pilot signal. 3 is a perspective view showing an example of a conventional video head, FIG. 4 is a partial plan view showing the main parts of the sliding surface, and FIG. 5 is a block diagram showing an example of a tracking error signal forming circuit. FIG. 3 is a characteristic diagram showing the relationship between the head position and the pilot signal reproduction level obtained when a pilot signal is recorded using a conventional video head and then reproduced. 1. FIG. 6 is a partial plan view showing the main part of the sliding surface of the first embodiment of the video head as a rotating magnetic head of the present invention, and FIG. 7 is a diagram showing a pilot signal recorded using the video head of the present invention. FIG. 8 is a partial plan view showing the main part of the sliding surface of the second embodiment of the video head of the present invention; FIG. 9 is a partial plan view showing the main part of the sliding surface of the third embodiment of the video head of the present invention. 1.22...Core, 6...Gap. Representative Patent Attorney Akio Takahashi No. 1, Rochitsukku, No. 3, No. 40! Fifth tyranny

Claims (2)

[Claims] (1) Rotation of a magnetic recording and reproducing device that records a pilot signal superimposed on a video signal or audio signal, and performs tracking control based on a tracking error signal obtained by detecting the pilot signal recorded on an adjacent track during playback. In the magnetic head, in addition to the main magnetic path of the gap formed on the opposing surfaces of the two cores, the same magnetic path as that formed on the opposing surfaces of the two cores is also provided on both sides of the gap in the longitudinal direction. A rotating magnetic head for a magnetic recording/reproducing device, characterized in that it has a structure in which a sub-magnetic path is formed. (2) In the rotating magnetic head, the width of one core is longer on both sides of the gap in the longitudinal direction than in the longitudinal direction of the gap formed on the opposing surfaces of two cores bonded together. A rotating magnetic head of a magnetic recording/reproducing apparatus according to claim 1.