JPS62159383A - Tracking device for rotary magnetic recording medium - Google Patents

Abstract

PURPOSE:To attain the optimum tracking control at either an inner or an outer circumference by providing a variable amplifying means. CONSTITUTION:Amplification degree in a variable gain amplifier 26 is set at a low level when a magnetic head 16 is positioned at the outer circumference of a recording surface on a magnetic disk 10, and a high level when it is positioned at the inner circumference. As a head position detection circuit 28, for example, a potentiometer constituted so as to change its output corresponding to the movement of the magnetic head 16, or an encoder, etc. is provided. An envelope detection circuit 30 detects the envelope of an FM modulation video signal recorded on the track of the magnetic disk 10, and outputs a corresponded DC voltage. A control circuit 32 receives the output of the envelope detection circuit 30, and controls a tracking motor 20 so that the output of the envelope detection circuit 30 becomes maximum at a requested track.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking device for a rotating magnetic recording medium.

[Prior art] Subject information is electronically captured as a still image using an imaging device such as a solid-state image sensor, recorded on a rotating magnetic disk, and a video signal is reproduced from the magnetic disk and displayed on a television monitor, video printer, etc. An electronic still camera system has been developed to reproduce this.

Recording media used for such magnetic recording, especially magnetic disks, suffer from poor tracking due to anisotropy, eccentricity, thermal expansion, etc., and during playback, glue and stalks from tracks adjacent to the target track are generated. There is a problem that occurs.

In order to avoid this problem, it is necessary to apply tracking servo during playback to optimally trace the playback head onto a desired track. Conventionally, a so-called mountain climbing method has been used as one method. This method applies tracking servo by detecting the envelope of the output signal from each track during playback and identifying the optimal tracking position from its peak position. This is because the optimal tracking position is when the magnetic head is near the positive peak of the envelope level. In practice, whether or not the magnetic head is near the peak is determined by the fact that there is virtually no difference in the envelope level between at least two adjacent head positions where the envelope level is above a certain value. be done.

[Problems to be Solved by the Invention] However, in devices such as electronic still cameras that perform recording and reproduction while rotating a magnetic disk at a constant speed, there is a magnetic difference between the outer circumference of the magnetic disk and its inner circumference. The relative speed between the head and the magnetic disk is different. For example, on an electronic still floppy (NTSC system), 7.5
It changes from 3m/S to 5.61111/S, and on the inner circumference,
The relative speed is about 25% lower than that at the outer circumference, and as a result, the reproduction signal level is also lowered. That is, as shown in FIG. 4, the level of the reproduction signal from the magnetic head is higher on the outer track than on the inner track.

Figure 5 shows this in relation to the off-track amount. If the horizontal axis is the off-track amount and the vertical axis is the playback signal level, when the off-track amount C is constant, the outer circumference For the track, the difference from the reproduced signal level at the center of the track is A, while for the inner track, it is 8. B is smaller than A, and therefore, appropriate tracking cannot be achieved by simply comparing the level difference between the reproduced signals at the two head positions with a certain reference value.

This corresponds to a decrease in magneto-electrical conversion gain when viewed as a system. If this continues, the amount of tracking error on the inner circumference will increase.

Additionally, if you increase the loop gain of the entire servo system to reduce the amount of error at the inner circumference, the increase in the feedback layer may cause long-lasting vibrations in the magnetic head, degrading the stability of the system. .

Therefore, in the conventional mountain climbing tracking method, tracking is performed by determining that the reproduced FM envelope level is above a certain value and that the envelope levels at two head positions near the peak are within a predetermined level difference. As mentioned above, the difference in the level of the reproduced signal envelope at the optimal tracking position is large between outer tracking and inner tracking, so if the determination level is constant, the tracking operation will be uncertain at either the outer or inner track. Become. Currently, when the envelope level exceeds a certain value at the outer periphery, it is clipped, but with this, the optimal tracking position cannot be detected and the best image cannot be reproduced.

In view of these problems, it is an object of the present invention to provide a rotating magnetic recording medium tracking device that can perform optimal tracking control on both the inner and outer circumferences of a rotating magnetic recording medium, particularly during reproduction thereof. shall be.

[Means for Solving the Problems] A tracking device according to the present invention includes, in addition to the conventional tracking device, a means for detecting the radial position of the magnetic head, and a means for detecting the radial position of the magnetic head, and detects the magnetic head from the magnetic recording medium with an amplification degree according to the position signal. A variable amplifying means is provided for amplifying the signal read by.

[Function] By adjusting the gain of the reproduction envelope detection amplifier in accordance with the track position being traced by the magnetic head, differences in reproduction output due to relative speed changes between the outer track and the inner track are eliminated. Then, regarding the track of interest, the position where the maximum output level is obtained is detected, and tracking of the magnetic head is performed. As a result, the best reproduced image can be obtained by tracking at any radial position.

[Example] An embodiment of the present invention shown in the drawings will be described below.

FIG. 1 shows a block diagram of an embodiment of a tracking device according to the present invention. In the apparatus of this embodiment, a rotating recording medium 10 such as a magnetic disk is driven by a spindle motor 1.
It is detachably attached to 2. The magnetic disk 10 has a magnetic recording sheet, and on its recording surface, a plurality of recording tracks are prepared concentrically at regular intervals. In this embodiment, the recorded signal is a video signal, which is, for example, a color video signal in which a luminance signal and a chroma signal are frequency-modulated. The spindle motor 12 is controlled by a spindle servo circuit 14 so that the magnetic disk 10 rotates at a predetermined rotational speed, for example, 3,600 rpm. A magnetic head 16 is mounted on the recording surface of the magnetic disk 10.
is disposed and carried on a support mechanism 18. This support mechanism 18 is driven by a tracking motor 20, and is configured to move the magnetic head 16 in both radial directions along the recording surface of the magnetic disk 10 to select any track on the recording surface. ing.

The reproduction output of the magnetic head 16 is amplified by a head amplifier 22, and the amplified output is connected to a video signal processing circuit 24 and a variable gain amplifier 26. The video signal processing circuit 24 is a circuit that processes the video signal detected by the magnetic head 16 and outputs it as a composite color video signal in, for example, NTSC format. The variable gain amplifier 26 amplifies the output of the head amplifier 22, and the degree of amplification changes depending on the output of the head position detection circuit 28 that detects the radial position of the magnetic head 16 on the recording surface of the magnetic disk 10. Basically, when the magnetic head 16 is located on the outer periphery of the recording surface of the magnetic disk 10, the amplification degree is lowered, and when it is located on the inner periphery, the amplification degree is increased. The head position detection circuit 28 includes, for example, a potentiometer or an encoder configured to change its output in accordance with the movement of the magnetic head 16.

The envelope detection circuit 30 is a detection circuit that detects an envelope of an FM modulated video signal recorded on a track of the magnetic disk 10 and outputs a DC voltage corresponding to the envelope.

The control circuit 32 receives the output of the envelope detection circuit 30 and detects the output of the envelope detection circuit 30 on a desired track.
The tracking motor 20 is controlled so that the output of the tracking motor 20 is maximized.

FIG. 2 shows an example in which the head position detection circuit 28 is implemented using a potentiometer. One end of the resistance wire of the potentiometer 40 is connected to a power supply, the other end is connected to ground, and the electrical output of the slider 42 is connected to the gain control input of the variable gain amplifier 26. is mechanically connected to the magnetic head 16 itself or its supporting portion, so that when the magnetic head 16 moves, the slider 42 also moves correspondingly.

Such a variable gain amplifier has an envelope detection circuit 3.
It may be connected after 0. This is shown in FIG. In this case, the gain will be changed so that the left-sloping straight line shown in FIG. 4 becomes a horizontal straight line that does not depend on the rack position.

[Effects of the Invention] According to the present invention, the same envelope level can be obtained at the center of all recording tracks regardless of whether they are outer tracks or inner tracks, so the peak position of the envelope can be reliably detected. Therefore, good tracking control can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
FIG. 3 is a partial block diagram of a modified example of the present invention; FIG. 4 is a diagram showing the relationship between the reproduction signal level and track position; FIG. 5 is a diagram showing an example of a head position detection circuit;・
FIG. 7 is a diagram comparing changes in reproduction signal level with respect to track amount between outer tracks and inner tracks.

Claims (3)

[Claims] (1) A magnetic head for reading signals from a rotating magnetic recording medium having a plurality of concentric signal recording tracks, a magnetic head moving means for moving the magnetic head in the radial direction of the magnetic recording medium, and reading from the magnetic head. A rotating magnetic recording medium tracking device comprising an envelope detection means for envelope detection of a signal, and a control means for controlling the magnetic head moving means to track the magnetic head to a target track according to the output of the envelope detection means. , comprising magnetic head position detection means for detecting the position of the magnetic head, and variable amplification means whose amplification degree changes depending on the position signal detected by the detection means and amplifies the signal read by the magnetic head. A tracking device for a rotating magnetic recording medium, characterized in that: (2) A tracking device for a rotating magnetic recording medium according to claim (1), wherein the output of the variable amplification means is input to the envelope detection means. (3) The tracking device for a rotating magnetic recording medium according to claim (1), wherein the output of the envelope detection means is input to the variable amplification means.