JPH01125704A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce drop-out of a reproduced pulse and to obtain relatively accurate reproduced data by generating a delay peak point by a delay peak pulse generating means after detecting reduction from a peak point by a prescribed value by a gate pulse generation means. CONSTITUTION:A reproduced pulse generating circuit 5 generates a reproduced pulse in response to generation of the delay peak point in a delay peak pulse generating means 3 after detection of reduction from the peak point by a prescribed value in a gate pulse generating circuit 4 and generates a reproduced pulse (d) in response to detection of reduction from the peak point by the prescribed value in the gate pulse generating circuit 4 after generation of the delay peak pulse in the delay peak pulse generating means 3. That is, the delay of the reproduced pulse, which is obtained in accordance with a dulled peal, from the rise of the delay peak pulse is compensated, and the existence of the other reproduced pulses in a prescribed window is secured. Thus, the possibility of drop-out of reproduced pulses is reduced to obtain more correct reproduced data.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus, and more particularly to a magnetic recording and reproducing apparatus suitable for reproducing signals written on a magnetic disk.

In a conventional magnetic recording/reproducing device, a peak pulse that inverts in response to the peak point of an analog signal read by a magnetic head is held for a predetermined period of time (this time is used for the next gate pulse in the gate pulse described later). (Determined empirically within the time just before the pulse reverses.)
By using a delayed peak pulse signal obtained by delaying the analog signal by a certain amount and a gate pulse that is inverted in response to a predetermined decrease in magnitude from the peak point of the analog signal, the gate pulse is set at the rising edge of the delayed peak pulse. Reproduction data was obtained by setting the reproduction pulse to 1'' when the gate pulse was 0'' at the falling edge of the delayed peak pulse.

However, in recording media such as magnetic disks,
Due to defects such as scratches, the peak point of the analog signal read by the magnetic head may become dull.
As a result, the time required for the analog signal to decrease by a predetermined amount from its peak point may be longer than in the case of a regular analog signal.

The longer the time required for the analog signal to decrease by a predetermined amount from the peak point, the slower the rise of the gate pulse signal becomes.

As a result, according to the conventional device, even if the gate pulse obtained from the regular analog signal becomes "1" at the rising edge of the delayed peak pulse, the gate pulse obtained from the blunted analog signal remains "0". Even if the gate pulse obtained by the regular analog signal becomes "0" at the falling edge of the delayed peak pulse, the gate pulse obtained by the blunted analog signal becomes "1".
In such a case, a reproduction pulse corresponding to the peak of the analog signal cannot be obtained, so there is a problem that correct reproduction data cannot necessarily be obtained.

In view of the above-mentioned problems in the conventional device, an object of the present invention is to prevent the gate pulse from rising in response to the rising edge of the gate pulse when the delayed peak pulse is "1" and the gate pulse rises after the rising edge of the delayed peak pulse. The concept is to form a reproduction pulse, and when the delayed peak pulse is 0'' and the gate pulse falls behind the falling edge of the delayed peak pulse, a reproduction pulse is formed in response to the falling edge of the gate pulse. Based on this, it is an object of the present invention to reduce the number of missing reproduction pulses in a magnetic recording and reproducing device, and to obtain relatively accurate reproduced data.

In the present invention, there is provided a magnetic head for reading signals written on a magnetic recording medium, a peak pulse generating means for detecting a peak point of a read signal read by the magnetic head, and a peak pulse generating means for detecting a peak point in response to the peak pulse generating means. delayed peak pulse generating means for delaying the peak point of the read signal for a predetermined period; gate pulse generating means for detecting the peak point of the read signal and detecting that the read signal has decreased by a predetermined value from the peak point; After detecting a decrease by a predetermined value from the peak point, the delayed peak pulse generating means generates a reproduction pulse in response to the generation of the delayed peak point, and the delayed peak pulse generating means generates a delayed peak pulse. a magnetic recording/reproducing apparatus comprising: reproduction pulse generating means for generating a reproduction pulse in response to the gate pulse generating means detecting that the gate pulse generating means has decreased by a predetermined value from the peak point after the peak point has been reached; is provided.

Embodiments of the present invention will be described based on FIGS. 1 and 2. FIG. 1 is a block circuit diagram of a magnetic recording/reproducing apparatus applied to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the apparatus of FIG. 1. As shown in the figure, an analog signal read out by a magnetic head 1 from a recording medium such as a magnetic disk is amplified to a required level by an amplifier 2, and the analog signal shown in FIG. 2a is obtained. The peak point of the waveform in FIG. 2a corresponds to mim of the data being written on the magnetic medium. In the portion marked ■ in FIG. 2a, the dotted line indicates a waveform when normally read, and the solid line indicates a waveform whose peak point is blunted due to a defect in the magnetic medium or the like. The analog signal shown in FIG. 2a is input to the peak pulse generation circuit 3. The peak pulse generation circuit 3 consists of, for example, a differentiating circuit that differentiates an input signal and a zero crossing circuit that generates a peak pulse corresponding to the zero crossing point of the output of this differentiating circuit. Figure 2.

As shown in FIG. 2A, in this embodiment, the peak pulse is inverted from "0" to "l" or from 1" to "0" corresponding to the peak point of the waveform in FIG. 2a. circuit 3
is the inverted signal of the peak pulse in Figure 2b.
2 peak pulses were also obtained. The peak pulses of tz and bz in FIG. 2 are appropriately delayed and sent to the peak pulse generation circuit 3.
A delayed peak pulse of b'l+1)Z in FIG. 2 is obtained at the output. On the other hand, the analog signal shown in FIG. 2a is also input to the gate pulse generation circuit 4. The gate pulse generation circuit 4 is composed of a drop detection circuit that generates a pulse that is inverted when the level decreases by a certain value or more from the peak point of the analog signal shown in FIG. 2a, for example. The method of obtaining zero or more delayed peak pulses and gate pulses, which provide gate pulses having an inverted relationship with each other as shown in FIG. 2 CI+02, is exactly the same as the conventional method.

In the part marked ■ in CI+CZ in Figure 2, the rise of the gate pulse obtained from the blunted analog signal (solid line in the figure) lags behind the rise of the gate pulse obtained from the regular analog signal (the dotted line waveform in the figure). This is what attracts attention. In order to obtain a reproduction pulse from the obtained delayed peak pulse and gate pulse, the above two types of pulses are input to the reproduction pulse generation circuit 5 according to the present invention. The reproduction pulse generation circuit 5 generates a reproduction pulse in response to the delayed peak pulse generation means generating the delayed peak point after the gate pulse generation circuit 4 detects that the predetermined value has decreased from the peak point. At the same time, after the delayed peak pulse is generated by the delayed peak pulse generating means, the gate pulse generating circuit 4 generates the reproduction pulse shown in FIG. It is meant to occur.

That is, in the reproduction pulse generating circuit 5, at the rising edge of the delayed peak pulse shown in FIG. 2b'1, the signals shown in FIG.
When the gate pulse of is in the state of "1°°" and at the rising edge of the delayed peak pulse of Fig. 2 b'8, Fig. 2 02
When the gate pulse of is in the "1" state, the reproduction pulse of FIG. 2 d is generated as in the conventional case, and the reproduction pulse of FIG.
When the delayed peak pulse of is “1°”, Fig. 2 01
When the gate pulse of rises and Fig. 2 b12
When the delayed peak pulse is “1°”, Fig. 2 02
A flip-flop (for example, Motorola's MCl0
f30).

As shown in the part ``■'' in Figure 2d, the reproduction pulse shown by the dotted line, which would be missing according to the conventional method, is
According to the present invention, the rise of the gate pulse corresponding to the blunted peak (the part marked ■ in FIG. 2 01) can be obtained with a slight delay without any dropout. The obtained reproduction pulse has temporal fluctuations due to pattern effects, which are characteristics of digital magnetic recording, and other noises. Therefore, as in the conventional method, the wind pulse (6++ez in FIG. 2) synchronized with the period of the reproduction pulse is transmitted to the phase synchronization circuit 6.
On the other hand, the mono multivibrator (delay circuit) in the phase synchronization circuit 6 and demodulator 7 adjusts the average position of the reproduced pulse so that it comes to the center position of the next wind pulse (see Fig. 2). d').

According to the present invention, since the regenerated pulse obtained corresponding to the blunted peak is obtained later than the rising edge of the delayed peak pulse, in another aspect of the present invention, the average position of the regenerated pulse is at the center of the wind pulse. It is adjusted so that it is located in front of the position (Fig. 2 d'').
In this case, the maximum value of the degree of adjustment is possible up to (wind pulse rtJ) - (time fluctuation due to pattern effect, noise, etc.), but in reality, a smaller value is selected. In this way, the reproduction pulse obtained in response to the blunted peak is compensated for being delayed from the rising edge of the delayed peak pulse, and by selecting the above-mentioned adjustment range, other reproduction pulses are also kept within a predetermined window. Therefore, it is possible to reduce the possibility of missing reproduction pulses and obtain more accurate reproduction data.

Incidentally, such adjustment of the position of the reproduced pulse is performed by the mono multivibrator (delay circuit) provided in the phase synchronized circuit 6 and demodulator 7 (provided before the phase synchronized circuit 6 and demodulator 7). This can be done by adjusting the delay time appropriately.

The demodulator 7 determines whether or not the position of the reproduced pulse shown in FIG. 2 d' or d II thus obtained exists in the section where the wind pulse shown in FIG. It is discriminated in the same manner as in the past, and if the reproduced pulse exists in the 1'' interval of the wind pulse, the reproduced data is ``1'', otherwise it is ``0'' (FIG. 2 f), and the reproduced data is output from the demodulator 7. can get.

In the foregoing detailed description of the invention, the peak pulse,
Although the delayed peak pulse, gate pulse, and wind pulse are each formed by a pair of pulse trains having a mutually inverted relationship, the present invention is not limited to this, and each pulse may be formed by a single Nohalus example.

According to the present invention, a reproduction pulse is formed in response to the delayed peak pulse generation means generating the delayed peak point after the gate pulse generation means detects that the predetermined value has decreased from the peak point. A reproduction pulse is formed in response to the gate pulse generation means detecting that a predetermined value has decreased from the peak point after the delayed peak pulse is generated by the delayed peak pulse generation means, thereby preventing omission of the reproduction pulse. This results in relatively accurate playback data.

Further, according to the present invention, it is possible to compensate for the fact that the regenerated pulse obtained in response to the blunted peak lags behind the rising edge of the delayed peak pulse, and to ensure that other regenerated pulses also exist within a predetermined window. As a result, the possibility of missing reproduction pulses can be further reduced, and more accurate reproduction data can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a magnetic recording/reproducing device applied to the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and a amplifies the signal read by the magnetic head. analog signal, bI. b2 is the peak pulse, b' I + b'! is the delayed peak pulse, cl+c! is the gate pulse, d is the reproduction pulse, else! is a wind pulse, dZdlJ is a phase-adjusted reproduction pulse, and f is reproduction data. l...Magnetic head, 2...Amplifier, 3...
Peak pulse generation circuit, 4... Gate pulse generation circuit, 5... Reproduction pulse generation circuit, 6... Phase synchronization circuit, 7... Demodulator.

Claims (1)

[Scope of Claims] A magnetic head for reading signals written on a magnetic recording medium, a peak pulse generating means for detecting a peak point of a read signal read by the magnetic head, and a peak pulse generating means responsive to the peak pulse generating means. Delayed peak pulse generation means for delaying a detected peak point for a predetermined time; Gate pulse generation means for detecting the peak point of the read signal and detecting a decrease by a predetermined value from the peak point; and the gate pulse generation means. After detecting that the delayed peak pulse has decreased by a predetermined value from the peak point, the delayed peak pulse generating means generates a reproduction pulse in response to the generation of the delayed peak point, and the delayed peak pulse generating means generates a delayed peak pulse. reproduction pulse generation means for generating a reproduction pulse in response to the gate pulse generation means detecting that the gate pulse generation means has decreased by a predetermined value from the peak point after the generation of the reproduction pulse; and a period of the reproduction pulse generated by the reproduction pulse generation means. A magnetic recording and reproducing device comprising: a phase synchronization circuit that generates a wind pulse synchronized with a phase synchronization circuit; and a demodulator that demodulates the reproduction pulse by positioning the average position of the reproduction pulse ahead of the center position of the wind pulse. Device.