JPS6130338B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a rotating head type magnetic recording and reproducing device (hereinafter referred to as
(VTR), and is related to conventional general
Tracking during playback can be done by eliminating the need for the control head and control signal recording track used in VTRs, and using periodically inserted constant level signals such as the color burst signal that is essential for color signals. It is configured as follows.

The control structure of a normal helical scan VTR is such that the rotational phase of the rotary head and the phase of the vertical synchronization signal are synchronized during recording, and the video signal is recorded on a magnetic tape that is transported at a constant speed. At the same time, a signal (control signal) synchronized with the rotational phase of the rotary head is also recorded.
During reproduction, the reproduction control signal and the rotational phase of the rotary head or capstan motor are normally synchronized in phase so that the reproduction head faithfully scans the recording track. However, since the video track and the control signal synchronized with it are recorded at a certain distance on the tape, if the environmental conditions differ between recording and playback, for example, if the magnetic tape expands or contracts due to temperature changes, During reproduction, a track shift occurs in accordance with the amount of expansion/contraction, and the S/N of the reproduced video signal deteriorates. For this reason, normal VTRs are equipped with a volume (tracking volume) that corrects tracking deviations, but it is difficult for general users to manually adjust the tracking volume for each recording tape to make subtle adjustments. is difficult.

Several methods have been devised to automatically perform tracking control to solve these problems, and these methods can be broadly divided into those that use amplitude changes in the reproduced RF signal, those that use an auxiliary head, and those that record pilot signals. It can be classified into

The above method controls the amplitude of the RF signal to its maximum, but since the maximum value changes for each deck and recording tape, the preset method, in which the maximum value is set in advance, has problems, and A method in which the maximum value is held each time, and when the RF signal amplitude decreases by a predetermined voltage from the hold voltage, the control is performed again aiming at the maximum value, there is no stable point, and therefore the RF signal amplitude constantly changes around the maximum value. A control method that changes the amplitude must be used, and the repetition frequency of the amplitude change is undesirable because it appears as a wow in the audio signal in the case of a capstan servo, and as shaking on the screen in the case of a cylinder servo. . Furthermore, as seen in Japanese Unexamined Patent Publication No. 52-42319, there is a method in which the rotating head is vibrated perpendicularly to the scanning direction to utilize changes in the amplitude of the RF signal, but this requires new parts and is not a good idea. Not.

The above method is a method in which auxiliary heads for detecting track deviation are provided on both sides of the rotary head, but this method also requires the addition of new parts.

In the above method, as seen in Japanese Patent Laid-Open No. 49-52610, a pilot signal is recorded on each track so that they are not adjacent to each other in a direction perpendicular to the direction of extension of the recording track, and during playback, a level difference between the pilot signals is recorded. This method detects and performs tracking control, but it requires an extra recording circuit.

The present invention adopts a recording method that avoids horizontal synchronizing signals being lined up in a direction perpendicular to the track extension direction (H line up) between adjacent recording tracks. This is periodic information with a phase shift. For example, by detecting the level difference between color burst signals, a stable tracking control method is provided that does not require an extra pilot signal and does not require a control head or a control track.

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram showing a magnetization trajectory recorded on a magnetic tape. The magnetization loci of the two-head helical scan VTR used in this example are actually recorded obliquely on the magnetic tape, but in FIG. 1, the magnetic tracks T ₁ , T 2 , T ₂ ,
T ₃ is shown. H ₁ , H ₂ , and H ₃ indicate horizontal synchronization signals, and FIG. 1 shows magnetization trajectories arranged in H order.

FIG. 2 shows the magnetization trajectory when partially overlapping writing is performed with a head having a head width _W2 . That is, T ₂ is recorded while erasing a part of the initial recording trajectory T ₁ , T ₃ is recorded while erasing a part of T ₂ , and the same operation is repeated thereafter. Therefore, the actual track width is
T ₁ ′, T ₂ ′T ₃ ′. By adopting such a recording method, three tracks can be scanned simultaneously during reproduction.

FIG. 3 shows a track in which the H alignment is recorded with a shift of 1/4 of the horizontal synchronizing signal interval. This can be easily accomplished by making the tape speed during recording faster (or slower) than the speed when recording in H arrangement. Further, the recording locus shown in FIG. 3 shows partially overlapping writing as in FIG. 2, and therefore the reproducing head width _W3 is somewhat larger than the recording track width. In reality, if each track is recorded adjacent to each other as shown in Figures 1 to 3, when the signal is played back across the adjacent track, the video signal and color signal of the main track will be recorded adjacently. This is undesirable as it is disturbed by the crosstalk signal from the track and appears as noise on the playback screen, but this crosstalk component can be removed by using the recording method described later, so here we will focus on the influence of adjacent tracks. Let's proceed as if there is no such thing.

Now, if the playback head faithfully reproduces the recorded track in Fig. 1, by performing appropriate signal processing, the playback signal can naturally be the same as the recorded signal, and of the playback signal, the color signal FIG. 4 shows the waveform obtained by separating only the signal. In FIG. 4, Vs indicates a vertical synchronization signal. Note that although the actual color signal system does not include a vertical synchronizing signal, it is shown here superimposed on the color signal for convenience of representing relative position. The signals necessary for the picture start from a position delayed by about 20H after the vertical synchronization signal, and the burst signal and color signal are included in the section shown in FIG. 42. Between the vertical synchronizing signal and the section 42, only a burst signal 43 is provided as a signal in order to improve the rise of the APC.
FIG. 5a shows a part of section 41 in FIG. 4 extracted. In the figure, 43 represents a color burst signal. Next, let us consider the case where a recording track that is not arranged in an H arrangement as shown in Fig. 3 is played back using a head that is slightly wider than the track width.
When W ₃ is reproduced equally across tracks T ₁ ′ and T ₃ ′, the color burst signal is such that the T ₁ ′ burst signal 44 and the T ₃ ′ burst signal 45 have different phases, respectively, as shown in FIG. 5b. appear differently. Further, FIGS. 5c and 5d show the burst signals when the head width W ₃ in FIG. 3 is reproduced by extending over T ₁ ' and when the head width W 3 is reproduced by extending over T ₃ ', respectively.

As is clear from the above explanation, when the reproducing head scans with a deviation from the main track T ₂ ', the direction of the deviation of the reproducing head can be detected based on the phase relationship with respect to the main burst signal 43, while the amount of deviation can be determined from the burst signal. It can be determined by the amplitude of 44 or 45. Therefore, tracking control can be performed by using the burst signal as a tracking deviation detection signal.

Next, a recording and reproducing method for removing interference from adjacent tracks will be described. So far, we have described a magnetization pattern with a head gap in a direction perpendicular to the direction of track extension, but in reality, the gaps of magnetic heads for recording and reproducing adjacent tracks are in opposite directions with respect to the perpendicular direction. A so-called azimuth recording is performed, which is configured to have an angle (azimuth angle). At this time, FIG. 3 becomes as shown in FIG. 6. In FIG. 6, the positions of the centers P ₁ , P ₂ , P ₃ of the horizontal synchronizing signals H ₁ , H ₂ , H ₃ of each track are shifted by 1/4H to correspond to FIG. 3. If such azimuth recording is performed, even if the playback head straddles tracks on both sides other than the main track, the FM-modulated luminance signals contained in the tracks on both sides have a high frequency and will be attenuated as azimuth loss. It does not affect the brightness signal of the main track. On the other hand, since the frequency of the color signal recorded after low frequency conversion is low, only a small amount of azimuth loss occurs, and the color signal of the main track is interfered with by the crosstalk signal from the adjacent track. However, there is a method in which the spectrum of the color signal of the main track and the spectrum of the color signal of the adjacent track are recorded in a frequency interleaved relationship, and during playback, a comb filter is used to separate only the color signal of the main track. By doing so, interference caused by crosstalk signals from adjacent tracks can be removed even for color signals, and recording without guard bands as shown in FIG. 6 becomes possible. If the color signal before the above color signal processing is taken during reproduction, the burst signal shown in FIG. 5 can be obtained.

Next, taking a capstan servo circuit as an example, a specific control method using the burst signal will be described with reference to FIGS. 7 to 9. FIG. 7 is a block diagram showing one embodiment of the present invention, and FIGS. 8 and 9 show waveforms at various parts in FIG.

During playback, the color signal is input to the amplifier circuit through terminal 70 before passing through a comb filter that removes crosstalk signals from adjacent tracks. The amplified color signal is gated by a gate circuit 73 made from a reproduced vertical synchronizing signal inputted from a terminal 72, and several burst signals (three in this example) within the section 41 shown in FIG. 4 pass through. The signal becomes signal a. In the figure, 43 is the main track burst signal;
4 and 45 are burst signals obtained from the front and rear tracks adjacent to the main track, respectively. Fourth
The burst signals obtained from adjacent tracks within section 42 of the figure overlap in time with the color signal of the main track and have the same frequency, so they cannot be separated. Therefore, it is necessary to use the signal within section 41 for the track deviation detection burst signal, and the gate circuit 73 is for this purpose.The reason why several burst signals are gated is that the burst signal is This is to ensure that, in the case of deletion, if any burst signal in the gate is obtained, as will be described later, the finally obtained tracking error voltage will not be significantly disturbed.

Burst signals 44 and 45 obtained from tracks adjacent on both sides of the main track are separated by gate circuits 75 and 76, respectively, which are controlled by pulses generated from a reproduced horizontal synchronizing signal inputted from a terminal 74, and The signals are rectified by D ₁ and D ₂ to become signals b and c. In the figure, 44' and 45' are the burst signals after being rectified. These signals are input to clamp circuits 77 and 78, resulting in signals a and b shown in FIG. Therefore, if the tracking during reproduction is deviated, the amplitude of the burst signal 44' or 45' increases or decreases, and eventually the values of the DC voltages V ₁ and V ₂ change. It is clear from the previous explanation that the values of V ₁ and V ₂ increase and decrease contrary to each other, and whether there are one or three burst signals 44' and 45', if they have the same amplitude, they will be equal to V ₁ and V _2. The fact that the influence is small can be easily considered from the nature of the clamp circuit. Conversely, if several burst signals are used for tracking error detection, any burst signal in the gate circuit 72 can be detected even when part of the burst signal is missing due to dropout or the like. Tracking error voltage V ₁ , V ₂
It can be said that the impact on

The error signals a and b are converted into more perfect DC voltages through filters 79 and 80 and input to a comparator circuit 81.

In FIG. 7, 82 is a capstan motor, 83 is a frequency generator (FG) directly connected to the motor shaft, 84 is a detection head, and 85 is a speed control circuit. The speed control circuit 85 compares the period of the AC signal obtained from the FG with the constant delay time of the monostable multi-channel signal triggered by the signal, and controls the motor 82.
This is a well-known speed control circuit that keeps the rotation speed of the motor constant. Therefore, it is sufficient to vary the delay time of the monostable multi-circuit using the tracking error voltage obtained from the comparator circuit 81. For example, when V ₁ and V ₂ shown in FIG. 9 become equal, the rotation speed of the capstan motor 82 is set near the normal rotation speed at which the rotary head on-tracks, and when the tape speed is slower than the normal speed. The comparator circuit is configured to increase the rotation speed of the capstan motor 82 if V ₁ >V ₂ due to mistracking of the rotating head, and to slow down the rotation speed of the capstan motor 82 if V ₁ <V ₂ . 81, the capstan motor rotates stably at V ₁ =V ₂ , that is, the rotary head tracks on-track and scans over the recording track.

As is clear from the above explanation, by choosing a tape format that does not have an H-alignment, it is possible to
By obtaining the color signal from the color signal processing circuit required for the control head and using simple circuits such as gates, clamps, filters, and comparison circuits, there is no need to record or reproduce extra pilot signals. Also eliminates the need for control tracks, capstan servo phase comparison circuits, etc.
Tracking control can be performed automatically.

In addition, in this example, a capstan servo is used.
Although only VTRs have been described, it can be easily inferred that the invention can also be applied to VTRs that use a rotating head servo.

In addition, in this example, the stable point was explained as the time when the rotary head scans astride tracks adjacent to both sides of the main track, but when the rotary head scans astride the main track and a track on one side adjacent to the main track. It can also be easily considered that is the stable point. At this time, when the amplitude of the burst signal obtained from the track on one side is at a certain level,
The rotational speed of the capstan motor may be set near the normal rotational speed at which the rotary head on-tracks, and the capstan motor may be accelerated or decelerated by increasing or decreasing the amplitude of the burst signal from a certain level.

Furthermore, although a color burst signal is used as a control signal in this example, the ViR (Vertical Interval Reference) inserted at the 19th H after the vertical synchronization signal
It is clear that similar control can be performed using a color reference signal having the same frequency as the color burst signal in the signal.

[Brief explanation of the drawing]

Figure 1 shows the magnetization trajectory of a normal VTR with H arrangement, Figure 2 shows the magnetization trajectory when superimposed writing is performed in Fig. 1, and Figure 3 shows superimposition without H arrangement. A diagram showing the magnetization trajectory when writing,
Figure 4 is a diagram schematically showing a color signal, Figure 5 is a diagram showing a color burst signal that changes due to track deviation during playback, and Figure 6 is a diagram showing a color burst signal that changes due to track deviation during playback. Fig. 7 is a block diagram showing an embodiment of the present invention; Fig. 8 shows the magnetization trajectory when
This figure and FIG. 9 are diagrams showing waveforms of various parts in FIG. 7. 70...Reproduction color signal input terminal, 73,7
4, 75... Gate circuit, 77, 78... Clamp circuit, 79, 80... Filter, 81... Comparison circuit, 82... Capstan motor, 83...
Frequency generator, 85...speed control circuit.

Claims (1)

[Claims] 1. Horizontal synchronization signals on the recording trajectories of color television signals recorded adjacent to each other are recorded so that they are not lined up in a direction perpendicular to the extending direction of the recording trajectories, and the deviation amount is greater than the width of the horizontal synchronization pulse. At least two or more color lines located in the 20H period immediately after the vertical synchronization signal in which there is no image information signal, which are recorded with the main scanning track and reproduced from each recording trajectory adjacent to the front and rear of the main scanning track. A tracking control device for a magnetic recording and reproducing device, which controls the relative phase between a reproducing head and a recording medium using changes in the level of a burst signal.