JPH0478054A - Autotracking circuit - Google Patents

Abstract

PURPOSE:To form a stable reproduced picture by expanding a noise pull-in ranger after making a tape traveling phase changing state takes its one round. CONSTITUTION:After the tape traveling phase changing state takes its one round, namely when a tracking control means 7 changes a tracking center value ten times for instance, an initial reference value is changed. For this purpose, after the tracking control means 7 changes the tracking center value ten times, it inputs a reference value changing pulse to a reference value setting means 8, and the reference value setting means 8 changes the initial reference value, and if the pull-in of a noise can not executed in this expanded noise pull-in range, the reference value is increased, and the noise pull-in range is continued to be expanded until the noise pull-in is completed. Thus, a desirable tracking state is detected irrespective of a recording state or a reproducing state, and the reproduced picture comes to be stabilized.

Description

Detailed Description of the Invention (a) Field of Industrial Application The present invention relates to an auto tracking/king circuit employed in a helical scan type magnetic recording/reproducing device. Kaihei 1-288184, HO4\
5/'783), auto-tracking is used to change the running phase of the tape during special playback to displace the portion where the playback output level of the video head drops (the noise portion) within the reference period from the head output switching timing. proposed a circuit.

(c) Problems to be Solved by the Invention However, when performing auto-tracking using a video tape recorder that employs the above-mentioned configuration, it may be difficult to displace the portion where the playback level drops within the reference period. be.

The cause of this is an abnormality in the contact state of the rotary head with respect to the tape at the beginning of scanning, or an abnormality in the linearity of the recording track.

Therefore, if auto-tracking is executed in such playback conditions, the tape running phase will continue to change, resulting in constantly changing tracking conditions - creating an unstable playback screen. (d) Solved the problem. Therefore, the present invention: In an auto-tracking/l-king circuit that sequentially changes the tape running phase state so that the portion where the playback output decreases is within the recording range, the tape running phase changing state is changed once. It is characterized by expanding the noise pulling range after setting.

(e) According to the present invention, after noise entrainment control, (2)
Noise attraction control is executed again with the elbow in the expanded noise attraction range.

(f) Example Hereinafter, two embodiments illustrating the present invention will be described.

Embodiment: The present invention is adopted in an auto-tracking/king circuit of an XH5 type video Q7 recorder which pulls the playback output level drop part into the noise pull-in range during double-speed playback, as shown in FIG. A schematic block diagram of its main parts is shown.

As is clear from FIG. 1, this embodiment mainly uses
To this master, the regeneration 8 force obtained by scanning alternately the regeneration-only secondary set 180 degrees against the elbow with the MH and azimuth in common, and the regeneration force 7. A head switching circuit 1 is configured to alternately select and convert the reproduction output into a continuous reproduction signal according to the head output switching pulse RF. The reproduced signal is amplified by the AGC Asia 2, and then input to the video signal processing circuit 3, and is also input to the dropout detection circuit 4 (inputted by two people).

The dropout detection circuit 4 generates a dropout detection pulse that becomes low level during the attenuation portion of the reproduction signal level, that is, during the noise generation period during double speed reproduction.

The noise position sampling means 5 counts the period from the rise of the head output switching pulse RF to the rise of the out detection valve 1 of the toro 77 at a frequency of 2 kHz.

This count value is used as a comparison input to the noise position comparison means 6 of the microcomputer. The noise position comparison means 6 compares the count value with the reference value generated by the reference value generation means 8.
If it is less than 1 standard value: It is considered that the noise extraction is complete.
generates a signal to fix the tracking center value -115
If it is less than -115, a signal that changes the tracking center value by -3 is generated. If it is -115 or more, t''L generates a signal that changes the trunking center value by +3.

The tracking control means 7 continues to sequentially change the tracking center value to be output in accordance with the output of the noise position comparison means I'i) in 3 steps until the noise pull-in state is reached. The control signal generated by the control head CH is delayed according to the value, and this delayed signal is fed to the caster stan servo 10 as a reference input f.

Therefore, the cafstan motor (1) to which the cafstan servo output is input continues to sequentially change the chive travel phase by a predetermined amount until it reaches the noise drawing state.

The waveform diagrams A1, A2, and A3 in Fig. 2 show changes in the reproduced signal output level in a normal noise drawing state.
1 indicates a state before noise capture, A2 indicates a state in the middle of noise capture, and A3 indicates a state where noise capture is completed.

As is clear from the figure, when noise extraction is completed in a normal state, all noise components are eliminated.

On the other hand, waveform diagrams 31, B2, and B3 in FIG. 2 show changes in the output level of the reproduction signal used to control noise in a video tape recorder, where the reproduction output level tends to decrease at the start of scanning, and Bl is the noise B2 shows the state before the noise drawing, B2 shows the state in the middle of the drawing, and B3 shows the desired noise drawing state. As is clear from the figure, it can be seen that even in an abnormal state and in a desirable noise-drawing state, the noise component extends over the chair-drawing range.

Therefore, in such a state, the Qi 7 no L row phase state (,
;Continues changing without stopping.

In this example, even under such conditions, the noise
Detects the entrainment state - Expands the noise entrainment range. This noise pull-in range is expanded by changing the initial reference value 131 to 4 after one cycle of the tape running phase change state, that is, when the trunking control means changes the tracking phase value 10 times. There is. Therefore, after the tracking/king control stage 7 changes the tracking center value 0 times, a reference value change pulse is input to the reference value setting means 8, and the base $f+lff setting means 8 is set to the initial reference value. Change the value -3,. to r4-.

Therefore, the reference value becomes 16' 4 J from now on, and in the case where noise acquisition is not possible within this expanded noise acquisition range, the reference value ([iF is increased by 1 and the noise acquisition is completed. Until then, the noise pull-in range will continue to be expanded.

As a result, as shown in C1, C2, and C3, respectively, the noise pull-in range is expanded.

The detection output within the mouth/fa is immediately the noise generating part;;/' The fL included within the nose pull-in range becomes 2.

3rd U'+::, micro-collector real movement point T, as is clear from the second figure showing the flow yard showing the j order, the playback mode is at double speed in the first stage Sl. First decide whether the mode is good or not! , then the th? S+・7S
2 sets the base $ value m to -3-. Fumiji, 3rd stage/
Set the number of changes to 7S3 to 0! , In the 4th step / 7S4, set the l-ra king center value to the initial 11JI value. Count value or 1. ) Determine whether or not L is less than or equal to t'
L is the 10th step 7510 and the tracking center f direct is 3 steps 2. -7 increase- to 117th. Moving on to Te 7, if it is less than 7, the count value I] is further m
Determine whether or not -1n>m If it is, the 9th step/block S9 subtracts the tiger king center value by 3 steps by 17.
When the state shifts to 1st step, T]≦mtfz is regarded as a tracking pull-in state, and the tracking center value is fixed in the 8th step, and the process ends.

In the 11th step 51.1, j updates the tracking f direct change number X, and in the 12th step/7, the updated value X is []0.''
If it is less than -101, the process returns to the fifth step, and if it is rlo-, the process returns to the 13th step 51.
3 updates the reference value, returns to the third stage S3 and starts the noise bow cutting control from the initial state.

-1- As described above, according to this embodiment, the tape running phase is shifted by 3 steps, and each time the shift goes around, the noise entrainment range is expanded by one step/step, so that the noise entrainment state is always detected. No.

(G) Effects of the Invention According to the present invention, by expanding the noise pulling range, a desirable tracking state is detected regardless of the recording state or playback state, and the playback screen becomes stable. It's large.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram according to the first embodiment of the present invention, and FIG.
Figure J is an explanatory diagram of the re-drop signal waveform, and Section 3' is an explanatory diagram of the microcomputer's operating procedure. −、）口、・7 out detection circuit

Claims (2)

[Claims] (1) In a helical scan type magnetic recording and reproducing device that sequentially changes the running phase of the tape in order to control the reduced playback output portion of the rotary head by bringing it within the noise drawing range, the state of changing the running phase is made one cycle. An auto-tracking circuit characterized in that the noise drawing range is later expanded. (2) A dropout detection circuit that generates a dropout detection output during the reproduction output attenuation period of the rotary head, and a counting means that counts the period from the head output switching timing to the dropout detection output deactivation timing using a constant frequency clock. and a changing means for comparing the counted value with a reference value and sequentially changing the running and transporting state of the tape until the counted value becomes less than the reference value. An auto-tracking circuit characterized in that it includes a reference value setting means for changing the reference value to a larger value after one cycle of changing the tracking state.