JPH02125584A - Tracking method for magnetic recording and reproduction device - Google Patents

Abstract

PURPOSE:To set a tracking value in response to each vari-speed reproduction mode and to eliminate the need for the tracking adjustment by adding a correction in response to each vari-speed reproduction mode to an optimum tracking value at the normal reproduction. CONSTITUTION:A delay time T' of a tracking monostable multivibrator in a servo circuit 13 is set by outputting a (1/2)T being the result of multiplying a constant 1/2 with a tracking value T at normal reproduction serially to a servo circuit 13 at double speed reproduction. A time till a tape is stopped is T2 at slow reproduction and the distance on the tape moved for the time T2 is X. Thus, the relation of position between a control pulse and a head depends on the value X and the noise on the screen is minimized at a value. Thus, the tracking adjustment is not required by keeping the relation of TB=(V '/V)T, where T is the tracking value at the normal reproduction and TB is the tracking value at slow reproduction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a helical scanning type magnetic reproducing device for reproducing television signals from tracks recorded diagonally with respect to the longitudinal direction of a magnetic tape. The present invention relates to a tracking method for a magnetic reproducing device for automatically obtaining an optimal tracking position during variable speed reproduction.

[Prior Art] When reproducing television signals recorded on a magnetic tape using a VTR, if the recorder and reproducing device are different, the image quality may be worse than when reproducing a self-recorded tape. This is both V
Since the mechanical precision and electrical precision between the TRs do not completely match, the video head does not accurately trace the center line of the recording trajectory of the tape, resulting in tracking deviation, as shown in FIG. At this time, the user had to adjust the tracking position using the tracking adjustment switch while looking at the screen or the high-fidelity track level meter to the tracking position where the image quality would be the best.

Further, even during variable speed playback such as double speed playback and slow playback, the < + - l king adjustment is performed based on a constantly constant value that is corrected for a preset tracking value. For this reason, when playing back a tape recorded with @'s VTR, even if the compatibility is not correct and the tracking adjustment has been made, if the tape is played back at variable speed, the specified speed will be set regardless of the tracking state at that time. This will cause noise to appear on the screen.

For example, to describe in detail the conventional tracking adjustment during double-speed playback, in the timing chart during normal playback shown in FIG. 6, the tape speed is set to V m m /
s, the time of one frame is Fsec, and if the tracking mono multivibrator in the servo circuit is delayed by Tsec, then from the rise of the head switching signal (when the head of the 2nd channel touches the tape), the position of Xmm on the tape is 1 Assuming that there is a control pulse at

Here, in order to remove noise on the screen, it is necessary to keep the distance between the head switching signal and the control pulse on the tape constant. Performing double-speed playback when the relationship of Equation 0 holds true means doubling the tape speed, and in order to make X the same value at that time, the delay time T of the tracking mono multivibrator at double speed is required. ' to T
'=(1/2)T.

However, conventionally, the delay time of a tracking mono multivibrator was changed from T to T as a method of changing the delay time at double speed.
``The method of increasing time is adopted. However, here T
- Since time is a constant value, the relationship T' = T-T" = (1/2) T can only be established when a certain value is preset. If the tracking during normal playback is off, T When the value of T' is adjusted, T'=(1/2)T is not achieved, and noise occurs on the screen. Therefore, it is necessary to readjust the value of T when the speed is doubled.

Further, tracking adjustment during slow playback will be described in detail based on FIG. 7. First, slow playback basically performs noiseless still playback intermittently, and feeds the tape one frame at a time. As a tracking method, the tape speed is increased by applying an accelerating voltage from the tape stop layer to the capstan motor for a certain period of time using the five servo circuits, and then the servo circuit uses the detected control pulse on the tape as a trigger. Operate the slow tracking mono multivibrator.

Then, after the delay time (time constant) Tsec of the slow tracking mono-multivibrator has elapsed, a voltage with a polarity opposite to that during acceleration is applied to the capstan motor as a brake voltage for a certain period of time to rapidly stop the motor. By repeating these steps, the tape is moved intermittently by a certain length.

Tracking adjustment was performed by changing the positional relationship between the control pulse and the position where the tape stopped (position traced by the head) by varying the delay time T of the slow tracking mono-multivibrator. However, since the delay time of this slow tracking mono-multivibrator is a constant value, it is necessary to perform tracking adjustment in the same way as when playing at double speed.

[Problem M to be Solved by the Invention] As described above, in the conventional tracking method, even if the tracking adjustment has been made during normal playback, the tracking adjustment during variable speed playback requires correction to the preset value. In addition, because it was set to the specified speed, compatibility could not be obtained correctly when playing back tapes recorded on Ike's VTR at variable speeds.

This has the drawback that noise occurs on the playback screen, and tracking adjustment specifically for the variable speed playback mode is inevitably required.

The present invention has been made in order to solve the above-mentioned problems in the conventional example, and it is possible to eliminate the need for further tracking adjustment even in variable speed playback mode when tracking adjustment has been made during normal playback. The purpose of this invention is to provide a tracking method for a playback device.

[Means and effects for solving the problem] That is, according to the present invention, there is provided a servo circuit that can set a tracking value, which is a scanning position of a magnetic head with respect to a track on a magnetic tape on which a television signal is recorded, using digital data. In the tracking method of a magnetic reproducing device having 1, a tracking value of TA=(1/2>T is set in the servo circuit during double-speed reproduction with respect to the optimum tracking value T during normal reproduction, and TB=(V'/V
) There is provided a tracking method for a magnetic reproducing device, characterized in that tracking adjustment is performed by setting a tracking value T in the servo circuit.

Therefore, according to the present invention, by adding a correction value corresponding to each variable speed playback mode to the optimum tracking value during normal playback, a tracking value corresponding to each variable speed playback mode is set, and tracking adjustment is not required. do.

[Example] Hereinafter, the method of the present invention will be explained based on the illustrated structure. 2 is a diagram. For example, a two-channel video head and a two-channel audio head are supported on the drum 6 at predetermined intervals on its circumference, and the video signals recorded on the magnetic tape and the video signals on the magnetic tape are mounted on the drum 6. The high-fidelity audio FM signal recorded in the deep part of the track is played back.The played video and high-fidelity audio FM signal are sent to the system controller i-roller via a video signal amplifier 7 and an audio signal amplifier 8. The signal is input to a level detection circuit 9 serving as an interface circuit, and level detection is performed.

As the level detection circuit 9, the video or audio F
Select switch 1 for selecting one of the M signals
0, and an amplifier 1 that amplifies the selected FM reproduction signal.
The detector circuit 2 includes a detection circuit 2 that converts the output to a DC level, and an integrator 11 that integrates the FM playback signal converted to the DC level over a predetermined refined interval, for example, 1 frame. Level detection is performed between each frame.

The variable divider 11 includes an inverting amplifier 1 that inverts the output.
1a, and voltage control 0 that increases the output current as the input voltage is lower.
IIt flow source 11b and its output flow I! a capacitor llc that receives the head switching signal from the servo circuit 13 described in 1 as a reset signal via the capacitor lid, and an NP that controls charging and discharging of the capacitor 11c.
N) A system controller 1 which has a transistor 11e and an amplifier 11f that amplifies the charging voltage of the capacitor llc, integrates the FM level between one frame, for example, and which will be described later.
It is sent to the AD conversion input port of No.2.

That is, as shown in FIG. 2, the integrator 11 is reset by the head switching signal from the servo circuit 13,
The capacitor llc starts charging and discharges in response to the next head switching signal, but outputs the integral value at the time immediately before discharge to the AD conversion input port of the system controller 12. In the second I2I, when the head switching signal is turned on, the FM playback signal from the first channel head is integrated, and when it is turned off, the FM reproduction signal from the second channel head is integrated.
As a result, it is provided to the system controller 12 as an averaged sampling value of the FM reproduction signal for one frame.

Therefore, with the level detection circuit having the above configuration, sampling values of the reproduced FM signal during a predetermined integration interval 1, for example, 1 frame can be obtained without time delay.

Therefore, if the head switching signal used as the reset signal for the integral operation is synchronized with the tracking address value of the system controller that performs tracking adjustment by changing the relative position of the magnetic tape and the head, the level detection circuit 9 can control the sampling speed. Based on this, the optimal position for tracking during normal playback can be easily determined as described later.

Next, the operation of the system controller 12 having an auto-tracking function during normal playback will be described. First, the integrated value of the video and audio playback FM signals for one frame by the level detection circuit 9 is digitalized by the AD input port. When a condition for starting a predetermined tracking operation, which will be described later, is met, an optimum tracking position is automatically searched according to the processing means shown in the flowchart of FIG. A servo circuit 13 receives tracking serial data as a tracking address from the servo circuit 12, and sends a drive signal to the drum 6 and capstan 14 to change the relative position between the head and the magnetic tape in accordance with the tracking address. In addition, the pickup signal from the head on the drum 6 is inputted to send out a forward/throat switching signal.

The following cases can be considered as conditions for starting the auto tracking operation of the system controller 12.

(a> When playing the first magnetic tape after turning on the power (b) When playing the first magnetic tape after inserting the cassette/I card (C) During playback, the recording time mode (standard mode: SP' long mode: EP) is turned off. (d) If the reproduction control pulse is interrupted by 0.5 u or more; (e) If the FM level has decreased due to the same cause; if the deafness continues for 2 seconds or more; any of the above (a) to (e). In this case, there is also a possibility that the trunking is not correct, and the system controller 12 receives these detection signals and operates according to the flowchart in FIG. First, select switch 10 is switched to video 4 (step S2), and video FM signal 3 is input.

Next, the subroutine is run one step to obtain the video signal FM signal level corresponding to each tora-soking position, as shown in FIG. Both ends A.

B is determined (step S3) and the tracking addresses of A and B are stored. At this time, system controller 1
A switch switching signal is applied to the select switch 10 from 2 to the level detection circuit 9 as an interface circuit, and tracking serial data corresponding to the tracking address is applied to the servo circuit 14.
The servo circuit 13 changes tracking by sending drive signals to the drum 6 and capstan 14 to change the relative position of the head and tape according to the given tracking address.

Then, in step S4, it is determined whether or not an audio FM signal is recorded based on the output from the audio signal amplifier 8, and if it is not recorded, the tracking address is set to (A+B)/2 (step S5 ), the tracking address is transferred as serial data to the servo circuit 13 and the process ends (step S6). In other words, if the audio FM signal is not recorded on the magnetic tape, (A+B)/2 is transferred to the servo circuit 13 as the tracking address. Given that O1-) racking is done.

In step S4, if the audio F%l signal is recorded, the switch off ffi signal 3 is applied to the select switch switch 1o and the audio signal amplifier 811
Switch to 1 (step S7), L, bell detection circuit 9
Level detection is performed using the following steps, and the point where the level of the audio FM signal is the highest within the maximum level range A-B of the video FM signal is detected. In other words, the maximum search range of the level is A-
Step S8), 1 point B in Fig. 4.
In step S9), change the signal in the direction of the dot, pass the peak, and change it to point C, which is a predetermined level lower than the peak, to detect both ends C and D of the maximum level range of the audio FM signal (step S9), and store the tracking address. . When the maximum level range C-D of the audio FM signal exists between the maximum level range A-B of the video FM signal (step 10), set the tracking address to (C+D)/2.
(step 5ll), transfers the serial data to the servo circuit 13 and ends (step 512).On the other hand,
If the maximum level range C-D of the audio FM signal does not exist between the maximum level range A-B of the video FM signal, set the tracking address to the address where the FM level between A-8 is the maximum.Step 813 ), transfer the serial data to the servo circuit 13 and end (step 5
12).

The reason why the audio FM signal is given priority in such tracking position settings is that the peak positions of the video FM signal and the audio FM signal are often different from each other, and due to the headband width, the audio FM signal is given priority. FM
This is done in consideration of the fact that the audio FM signal has more problems than the audio FM signal, such as noise being more likely to occur, so it is possible to set the optimal tracking position that satisfies both the video and the audio.

Next, tracking adjustment during variable speed playback by the system controller will be described. first.

During double speed playback, it is necessary to set the delay time T' of the traction/soaking mono multivibrator in the servo circuit 13 to T'=<1/2)T, as is clear from the explanation of the conventional example mentioned above. , the system controller has a tracking value TA for double-speed playback, which is obtained by multiplying the tracking value T for normal playback obtained as described above by a constant of 1/2.
= (1/2) T is serially output to the servo circuit 13 and installed.

As a result, in the servo circuit 13, the delay time of the built-in tracking seven multivibrator is TA=(
1/2)T, the head switching signal shown in No. 612I is delayed by the delay time, and the control pulse is phase-compared, and the rotation of the capstan motor is controlled so that the difference becomes constant. , for the best tracking point T during normal playback, T, -(1/
2) Since the relationship between T is always maintained, there is no need for tracking adjustment.

Also, during slow playback, in Figure 7 mentioned above, the time from when the control pulse is generated until the tape stops is T, and the distance traveled on the tape during that time T2 is X. The value determines the positional relationship between the recontrol pulse and the head, and at a certain value, the noise on the screen is minimized.

Here, by changing the delay time T of the slow driver/l king seven-way multivibrator built into the servo circuit 13, T2 is changed, and therefore X is also changed to perform tracking j'l adjustment.

Therefore, if the tracking is off by X' during normal playback, tracking X during slow playback is the average tape speed in the interval T from detection of the control pulse to tape stop. Assuming V', X= (V' /V
) The relationship X holds true.

In other words, if this is obtained as the tracking value T during normal playback, and if the tracking value during slow playback is T8, the tracking adjustment can be made by maintaining the relationship T8=(v'/V)T. No longer needed.

In this embodiment, the system controller 12
As a result, the optimal tracking value T for normal playback can be obtained. Based on this, during slow playback, the value multiplied by the constant of V' and /V is serially output to the servo circuit 13 to obtain the double speed. Tracking adjustment is not required in the same way as during playback.

[Effects of the Invention] According to the tracking method of the magnetic reproducing device of the present invention, the optimal tracking value during normal playback is corrected by multiplying by a predetermined constant during double-speed playback and slow-speed playback, respectively, and the tracking value during variable-speed playback is obtained. Since this is set in the servo circuit, tracking adjustment during variable speed playback is not required, and operability can be improved.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing a magnetic reproducing device implementing the method of the present invention, Fig. 2 is an explanatory waveform diagram of level detection by a level detection circuit, Fig. 3 is an operation flow chart of the system controller, and Fig. 4 is a tracking diagram. FIG. 5 is a characteristic diagram for explaining position setting, FIG. 5 is a diagram for explaining tracking deviation, and FIGS. 6 and 7 are signal waveform diagrams for explaining the conventional example and the present invention in detail. 2... Detection circuit, 6... Drum, 9... Level detection circuit, 12... System controller,
13... Servo circuit, 14... Capstan. Inventor Michinori Shibuya Patent author Victor Japan Co., Ltd. Agent

Claims (1)

[Claims] In the tracking method of a magnetic playback device that has a servo circuit that can set the tracking value, which is the scanning position of the magnetic head with respect to a track on which a television signal is recorded on a magnetic tape, using digital data, the optimum tracking value T during normal playback is set. On the other hand, when playing at double speed, T_A=(
1/2) A tracking value T is set in the servo circuit, and during slow playback, the magnetic tape speed during normal playback is set to V', and the tracking value is A tracking method for a magnetic reproducing apparatus, characterized in that tracking adjustment is performed by setting a tracking value of T_B=(V'/V)T in the servo circuit, where V is the speed of the magnetic tape.