JPH0366053A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To accurately perform tracking control even though the output of a head is change by switching sensitivity or gain corresponding to the output level of the head, converting the output of the head to a DC voltage within a fixed extent and outputting it to a servo circuit. CONSTITUTION:The output of a head amplifier 23 is divided into three areas corresponding to the level; a demagnetization area, a normal area and high output area, and the output of the head amplifier is converted to the DC voltage within a fixed voltage extent and outputted to the servo circuit 12 by an A/D conversion circuit 11 provided with a sensitivity switch. And also a change in characteristics is detected based on a level change in the D/C voltage and the signal of commanding characteristic switching is outputted so that the characteristic may be specified by the circuit 12. Thus, by converting the output of the head amplifier to the D/C voltage corresponding to the output level of the head amplifier and performing the automatic tracking control, the tracking control can be accurately performed even though the output of the head amplifier is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording/reproducing device having an auto-tracking function.

Conventional technology The auto-tracking method of conventional magnetic recording and reproducing devices is
This will be explained based on the 10-step diagram in Figure 1.

Since the signal read by the video head 21 has a very low level, it is amplified by the head amplifier circuit 23.
On the one hand, the signal is supplied to the video signal processing circuit 24 and reproduced to the original video signal, and on the other hand, it is supplied to the Φ conversion circuit 25 where it is converted into a DC voltage and supplied to the servo circuit 27 .

The servo circuit 27 inputs the head amplifier output converted into DC voltage and the control signal detected by the control head 22 as a control signal, and controls the cylinder motor 2.
8 FG (frequency generator) frequency signal and PG
The cylinder motor 28 is controlled using the pulse signal of the pulse generator (pulse generator) as a feedback signal via the L cylinder driver 41 circuit 26, and the frequency signal of the capstan motor 300FG is used as a feedback signal to control the capstan motor 28 via the cadestand fip circuit 29. 30 to prevent image shaking and image disturbance due to uneven rotation.

The conversion characteristic between the DC voltage and the head amplifier output of the Φ conversion circuit 25 is shown by characteristic X in FIG. This characteristic X shows that when the head amplifier output is small, the DC voltage changes greatly,
This prevents the atb DC voltage from changing when the head amplifier output becomes thicker.

The reason why the conversion characteristics are as follows is shown below.

(2) Since the discrimination range of DC voltage in the servo circuit 27 is limited, it is necessary to use it effectively within that range.

■ When playing back a tape in relatively good condition, such as a self-edging tape, the head amplifier output increases, and even if the tracking accuracy is slightly poor, the playback image quality does not deteriorate much.

■ When playing tapes in poor condition such as demagnetized tapes,
The head amplifier output is originally at a small level, and even if the tracking shift amount is changed slightly, the maximum head amplifier output is small, so the amount of change in the converted DC voltage is small, making it difficult to control auto-tracking. .

For this reason, when the head amplifier output level is low, the amount of change in DC voltage is increased, and when the head amplifier output is high, the amount of change in DC voltage is decreased, and the signal is used as an auto-tracking control signal. Servo circuit 2
7, tracking control is best. In this way, the signal output from the head amplifier 21 and converted into a DC voltage is supplied to the servo circuit 1ii827, and control is performed to obtain optimal tracking. In front of the servo circuit, tracking is performed in the tape running direction, and control is performed so that the DC voltage converted from the output of the head amplifier is maximized so that the video head 21 on the rotating drum is always in the best tracking state. conduct. As described above, the conventional method employs an auto-tracking method in which the head amplifier output is simply converted into a DC voltage, and the tracking is changed so that this voltage is simply maximized.

Problems to be Solved by the Invention However, with the characteristic However, if the DC voltage shown in FIG. 4 were to have a characteristic Y that is simply proportional to the output direction of the head amplifier, there was a problem in that the tracking accuracy with the demagnetized tape would be insufficient.

Furthermore, there is a problem in that accurate auto-tracking accuracy cannot be obtained due to the voltage discrimination range and minimum voltage detection limit on the side of the controlling servo circuit 27.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording and reproducing apparatus that improves the accuracy of auto-tracking, which solves the above-mentioned problems.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a magnetic recording system equipped with a servo circuit having an auto-tracking function that automatically controls optimal tracking conditions when playing back a recorded tape. The playback device is equipped with a conversion circuit that switches the sensitivity or gain according to the video head output level, converts the video head output into a DC voltage within a certain DC voltage range, and outputs the DC voltage to the servo circuit. It is something.

Function: According to the above structure, the sensitivity or gain is always switched within the optimum range, and the video head amplifier output is varied by DC voltage, even on recorded tapes with bad wavy lines or tapes with relatively good recording conditions, such as self-edging tapes. As a result, the servo circuit can sufficiently recognize changes in the head amplifier output, and optimal tracking can be performed.

EXAMPLE An example of the present invention will be described below based on the drawings. Components that are the same as those in the conventional example shown in FIG.

FIG. 1 is a block diagram of a servo system of a magnetic recording/reproducing apparatus showing an embodiment of the present invention.

The magnetic recording/reproducing apparatus of the present invention replaces the conventional 00 conversion circuit 25 shown in FIG. 3 with a Φ conversion circuit 11 with sensitivity switching. The Φ conversion circuit 11 is divided into three parts as shown in Fig. 2, 1bl, and the characteristics for converting the head amplifier output into DC voltage are divided into three ranges, as shown in Fig. 2 (al), within the servo circuit voltage identification range. It switches to three characteristics a, b, and c and outputs them to the servo circuit 12.Also, when the servo circuit 12 detects, for example, a change from characteristic a to characteristic A by a change in the DC voltage level, In addition, a characteristic switching command signal specifying the characteristic can be outputted so that the characteristic of the Φ conversion circuit 11 is not changed to the characteristic a again.

In this way, if the output is converted to a DC voltage according to the head amplifier output level and used for auto-tracking control, the playback head amplifier output will change greatly from the demagnetized tape to the self-edge tape 1. Even under such conditions, tracking can be controlled with high precision. Among these, the control by the servo circuit 12 and the like are the same as in the conventional example, so the explanation will be omitted.

Also, this sensitivity can be changed by changing the gain of the head amplifier output. It may be 4.

Effects of the Invention As described above, according to the present invention, on-track conditions can be accurately obtained by switching the sensitivity or gain of the head amplifier output and outputting it to the servo circuit in response to changes in various conditions of the recorded tape. This allows for optimal tracking.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a servo system of a magnetic recording/reproducing device showing an embodiment of the present invention; Fig. 2 (a) and (b) are characteristic diagrams of the Φ conversion circuit with sensitivity switching shown in Fig. 1; FIG. 3 is a block diagram of a servo system of a conventional magnetic recording/reproducing apparatus, and FIG. 4 is a characteristic diagram of the non-Φ conversion circuit shown in FIG. DESCRIPTION OF SYMBOLS 11... Φ conversion circuit with sensitivity switching, 12... Servo circuit, 21... Video head, 22... Control head, 28... Cylinder motor, 30... Capstan motor.

Claims (1)

[Claims] 1. A magnetic recording and reproducing device equipped with a servo circuit that has an auto-tracking function that automatically controls optimal tracking conditions when playing back a recorded tape, and adjusts the sensitivity according to the video head output level. Alternatively, a magnetic recording/reproducing device is provided with a conversion circuit that switches the gain and converts the video head output into a DC voltage within a constant DC voltage range and outputs the DC voltage to the servo circuit.