JPS59231777A - Inter-track detector - Google Patents

Abstract

PURPOSE:To avoid the deterioration of reliability for the detection of a track even at a high-speed detection mode by driving a pulse generating means with the edge of a read reproduction signal undergone the shaping of waveform at a level higher than the threshold value only when the reading position exists on a track and therefore attaining the expression in a binary form. CONSTITUTION:A waveform shaping means 100 has the prescribed threshold value with a voltage source 300. A single pulse generating means 200 is driven by the edge of the output signal of the means 100. In case the reading position is set between the tracks, no signal is delivered since the level of the means 100 does not exceed its threshold value. In this case, the output potential is reset to its original level to detect an area between tracks in case the time taut is longer than the duration time taup of the pulse generated from the means 200. The read reproduction signal does not act as noise since it is changed into a rectangular wave. Thus the track can be retrieved at a high speed. The signal is produced once when an area between the tracks is crossed. Thus it is possible to detect the area between the tracks with high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an inter-track detection device used to search for a target track on an optical disk, magnetic disk, or the like.

2. Description of the Related Art Structures of Conventional Examples and Their Problems In recent years, directly accessible recording media such as optical disks and magnetic disks have been rapidly becoming popular. It can be said that the superiority of disks over other recording media is that they have both high information density and high speed retrieval.

The following methods are available for realizing high-speed search, which is one of the characteristics of discs. When searching for a track containing the desired information, know the number of tracks that exist between the initial reading position and the target track, and then move the reading position while counting the tracks that are currently being crossed. and reach the desired track. This means is called a track counter, and if the tracks crossed during the search can be detected without error,
It can be said that this is a means that can detect a target track at extremely high speed. In other words, the success or failure of the track counter depends on how reliably the inter-track detection is performed.

FIG. 1 shows a block diagram of a conventional track-to-track detection device. In the figure, reference numeral 110 denotes a band pass filter that removes high frequency components and DC bias components of the read and reproduced signal;
Reference numeral 11 denotes a comparison means for comparing the signal passed through the bandpass filter 110 with a ground potential, and 112 a gate circuit for determining whether or not to transfer the output signal of the comparison means 111 to a subsequent stage according to a control signal.

The operation of the conventional track-to-track detection device configured as described above will be described below. FIG. 2 shows a waveform diagram of a signal processed by the apparatus shown in FIG. (a) is a read reproduction signal. The above signal is obtained when a binary signal B written on a recording medium A is reproduced at a reading position C which can be moved relative to the recording medium A, as shown in FIG. During track search, no reproduction signal is obtained between tracks, so the level fluctuates as shown in the figure. Second
Figure (b) shows the input signal of the comparison means 2.

As a result of removing the high frequency and DC bias components by the bandpass filter 110, a signal that fluctuates around the ground potential according to the waveform envelope shown in FIG. 2(a) is obtained. Depending on the magnitude of this signal and the ground potential, the comparator 111 outputs a rectangular wave signal as shown in FIG. 2(C). Even when the signal detection position is constantly on the track, the low frequency component of the read and reproduced signal mixes as noise into the pass band of the band pass filter 1100, so that the comparing means 111 operates. Gate circuit 11
2 serves to transfer the output of the comparing means 111 to the subsequent circuit only during track searching.

By the way, in the above-mentioned conventional configuration, since noise is always mixed in the passband of the bandpass filter 110 as described above, the wider the passband is, the more the S/R of inter-track detection becomes
N gets worse. This means that if the moving speed of the detection position is increased to perform a high-speed track search, the fluctuation frequency of the envelope of the signal shown in Figure 2 (a), which is the target of extraction, will inevitably become higher. The passband of the bandpass filter 110 must be widened, and therefore inter-track detection is performed with a low S/N ratio, which lowers the reliability of inter-track detection during high-speed search. That is, as shown in FIG. 2(c), when the comparator 111 performs waveform shaping, chattering may occur and an erroneous inter-track detection signal may be output. Also, comparison means 11
1 operates even when the detection position is constantly on the track, as mentioned earlier, it is necessary to carefully open and close the gate circuit 112 at the timing shown in FIG. 2(d). Another problem was that the control circuit became complicated.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems.It is possible to always detect between tracks with high reliability even during high-speed search, and when the detected position is constantly on a track, the output is The object of the present invention is to provide an inter-track detection device that can emit a signal only once when crossing one track without changing the signal.

Structure of the Invention The present invention shapes read and reproduced signals extracted in time series from a recording medium having a track formed of an array of binary signals with a limited maximum inversion interval into a rectangular wave signal using a predetermined threshold value. a waveform shaping means; and a retrigger type single pulse generating means that is driven by the edge of the read reproduction signal shaped by the waveform shaping means and maintains the same potential for a time longer than the maximum edge interval of the shaped read reproduction signal. By driving the single pulse generating means at the edge of the read reproduction signal whose waveform has been shaped to exceed the threshold only when the reading position is on the track, the reading position is on the track and on the track respectively. An excellent track-to-track detection device that can express the case between troughs in binary terms and that does not reduce reliability even when the movement speed of the reading position is increased for high-speed search. It is.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 4 shows a basic block diagram of an inter-track detection device according to an embodiment of the present invention. In the same figure, 1
oO is a waveform shaping means having a predetermined threshold value 2 by a voltage source 300, and 200 is a retrigger type single pulse generation means driven by the edge of the output signal of the waveform shaping means 100.

The entire operation of the track amount detecting device of this embodiment constructed as described above will be explained below. Waveform shaping means 1
When the read and reproduced signal shown in FIG. 6(a) is input to 00, a rectangular wave as shown in FIG. formatted into. A square pulse generating means 20 is generated at the edge of the shaped read and reproduced signal.
0i drive. Now, assuming that the pulse generated by the single pulse generating means 200 maintains the same potential for a longer time (τp) than the maximum edge interval τmaX of the shaped read and reproduced signal, the next pulse will be generated before the potential returns to the original value. Since the edge is inserted, the output potential of the single pulse generating means 200 does not change after all.

Now, considering the case where the reading position is between the tracks, the fifth
As shown in Figure (a), during this period, the read and reproduced signal does not exceed the threshold of the waveform shaping means 100, so no signal is output as shown in Figure (b). During this time, when τt is longer than the duration τ of the pulse emitted by the single pulse generating means 200, the potential of the output returns to its original state, and therefore, the potential between the trunks is detected as the above potential. This situation is shown in Figure 5 (C).
Shown below.

As described above, according to this embodiment, the read and reproduced signal is made into a rectangular wave by the direct waveform shaping means 100, so that the read and reproduced signal does not act as noise unlike the conventional example, and as a result, the read and reproduced signal does not act as noise. Search speed can be increased. Furthermore, by applying the output of the waveform shaping means 100 to the single pulse generating means 200, the output signal does not change when the reading position is on a track, and only one signal is emitted when the reading position crosses one track. It is possible to realize an inter-track detection device that can perform the following steps.

Next, a second embodiment of the present invention will be described.

FIG. 6 shows a main circuit diagram of a specific embodiment of the present invention. In FIG. 6, 1 is a capacitor for removing the DC bias component of the read and reproduced signal, 101 is a comparison means, and 4, 7, 8.9 and 3°6.6 are a DC amplifier and a resistor that constitute the comparison means 101. be. 102 is a feedback means for determining the DC bias from the output of the comparison means 101; 10 and 11 are resistors connected to the power supply line and the ground respectively in order to obtain a reference voltage; 14 is a resistor 11 connected to the positive phase input terminal. 12 is a resistor connected to the negative phase input terminal as an input resistance of the operational amplifier 140, and 13 is an operational amplifier 14. A capacitor 15 and 16 constitutes an integration circuit together with a resistor 12. A resistor and a capacitor 15 and 16 constitute a first-order low-pass filter. A 2 is connected between the capacitor 1 and the comparison means 1010, and 17 is connected between the resistor 16 and the waveform shaping circuit 101. are resistors inserted in series with each. The comparison means 101 and the feedback means 102 constitute a reproduced signal punching means 104. 103 is a constant switching circuit; 21 is a resistor for changing the reference voltage inserted in series between the resistor 10 and the positive phase input terminal of the operational amplifier 14;
2 is a switch connected to both ends of the resistor 210; 23 is a resistor for switching the time constant inserted in series between the resistor 12 and the output end of the comparison means 101; 24 is a switch connected to both ends of the resistor 23. It is.

The waveform shaping means 100 is constituted by the above 101, 102, and 103. 200 is a single pulse generating means that is driven by the edge of the output of the comparing means 1o1 and generates a signal having a constant pulse width.

The operation of the inter-track detection device of this embodiment configured as described above will be explained below.

When the read reproduction signal shown in FIG. 7(a) is given an appropriate bias by passing through the capacitor 1 and the resistor 2 and is input to the comparison means 101, the threshold level is reached as shown in FIG. 7(b). It is shaped into a square wave punched out. Now, let us consider a case where a signal on a track is constantly being reproduced (hereinafter referred to as state A).

In this case, resistor 21 and resistor 23 are respectively connected to switch 2
2 and switch 24. Comparison means 101
and a reproduction signal punching means 104 comprising a feedback means 102.
The response frequency fCA of is generally given by the following equation.

fcp, “”o ・Gp/2πC13R12”””(1
), where % is the DC gain of the comparing means 101, and GF is GF-
Feedback means 102 given by R2/(R1, +R1□)
is the DC gain of Here, R2, R12, R15, R
1□.

C13 represents the resistance values of resistors 2, 12, and 15.17, and the capacity value of capacitor 13, respectively.

As shown in FIG. 7(C), the positive phase input terminal of the operational amplifier 14 is as follows: vA=DD-R11/(R1o+R11)
...It is at a potential expressed by (2). Here, Y
DD is a constant voltage. Therefore, feedback is applied so that the reproduced signal punching means 104 follows the response frequency fCA so that the negative phase input terminal of the operational amplifier 14 is always at vA. As a result, the output voltage (71)C of the operational amplifier 14
2 is applied as a bias to the input of the comparison means 1Q1 with a fixed threshold level, causing the read reproduction signal to rise or fall with respect to the threshold level, so that the output of the comparison means 101 TA=
The average value between 1/fA is controlled to always be vA. Figure 7 (
, ) is indicated by a broken line. 4. Here, consider the case where a track search is executed (hereinafter referred to as state B). In this case, since the reading position crosses between tracks, the read reproduction signal fluctuates as shown in FIG. 7(a). Let us consider a case where the moving speed of the reading position is sufficiently faster than the response of the reproduced signal punching means 104 and a case where it is sufficiently large.

In the former case, as shown by the broken line in Figure 7(a),
- Since the punching level also follows the decrease in the level of the read reproduction signal when the reading position crosses between tracks, even a noise level signal can be punched, as shown by the broken line in Figure (b). The signal is extracted and output as a rectangular wave, and as a result, the area between tracks is not detected as a no-signal portion. In addition, even if the moving speed of the reading position is sufficiently fast and the punching level does not follow the level fluctuation of the reading reproduction signal, feedback is applied so that the average value of the signal after punching always becomes the reference voltage. In the end, as shown by the broken line in FIG. 8(a) and FIG. 8(b), the punching level follows so as to fill in the gaps between the tracks, and the gaps between the tracks are not detected.

Now, when transitioning from state A to state B, this situation can be avoided by opening switch 22 and switch 24. That is, by opening the switch 24, the response frequency of the reproduced signal punching means 104 written in equation (1) becomes fCB expressed by the following equation, fcB=GOGF/2πC13(R12+R23).
...--: (3) It is possible to slow down the followability, and therefore, as mentioned above, the punching level does not follow the level fluctuation of the read reproduction signal when it crosses between tracks [Fig. 7 ( (a) Solid line] The area between tracks can be detected as a no-signal area. Furthermore, by opening the switch 22, the reference voltage becomes VB=VpD-R11/(R1°+R11+R21) as shown in FIG. 7(C).
"""('). This is because the reference voltage is set low in advance, assuming that the average value of the shaped waveform of the read and reproduced signal will decrease as a whole if no signal is detected between tracks. By doing this, the above-mentioned ``feedback'' that embeds the tracks does not occur, and therefore the spaces between the tracks are always empty as shown in FIG. 7(b) or FIG. 8(C). It will be detected as a signal part.

The edges of the thus shaped read and reproduced signal drive the single pulse generating means 200. Single pulse generating means 20
If the width of the pulse emitted from 0 is set sufficiently longer than the maximum edge interval of the read reproduction signal, when the read position as shown in Fig. 7 (b) and Fig. 8 (C) first crosses the track. As a result, if the no-signal portion between tracks is longer than the maximum edge interval, the shaping waveform generated only by A clearly distinguishable signal can be obtained.

As described above, according to this embodiment, the comparison means 101 punches the read reproduction signal at an appropriate threshold level, and the feedback means 102 determines the threshold level while comparing the average value of the output with the reference voltage. By adding a constant switching circuit 103i that lowers the response frequency and changes the reference voltage when searching for a track to the reproduced signal punching means 104 configured as shown in FIG. re-trigger type pulse generating means 20 which generates a signal having a pulse width of an appropriate length using the signal.
0 and connects all the shaping signals when the reading position is on the track, the pulse generating means 2 determines whether the reading position is on the track or between the tracks.
It can be clearly distinguished by the level of 00 output. Furthermore, although the circuit has a reproduction signal punching means 104'ii that can determine the threshold level by the feedback means 102 in order to cope with variations in the read reproduction signal due to differences in recording media, the above circuit is used when normally reproducing information on a track. Therefore, when performing a track search, only the constant switching circuit 103 and the single pulse generation means 200, which are composed of only a few switches and resistors, are required, and therefore the configuration can be very economical. A track-to-track detection device can be realized.

FIG. 9 shows a circuit diagram of essential parts showing another embodiment of the present invention. In the same figure, the parts other than the constant switching circuit indicated by 1o3' are completely the same as the embodiment shown in FIG. 6, and therefore not all are shown in the drawing. 32 is a resistor inserted between the output of the comparing means 101 and the input resistor 12 of the integrator, 33 is a switch connected to both ends of the resistor 32, and 31 is a resistor inserted between the connection point of the resistors 12 and 13 and the constant voltage source. is a resistor connected to

Next, the operation of this embodiment will be explained.

When reproducing the information on the track, the switch 33 is closed. If the output impedance of the comparing means 101 is sufficiently low, the influence of the resistor 31 can be completely ignored, and the result is completely equivalent to the case where the switches 22 and 24 are closed in the embodiment of FIG.

When searching for a track, the switch 33 is opened.

As a result, the response frequency fCC is fcc−9GF/”πC13(R12+R31/
R52)'-'(5). Here, R31/R3□ represents the parallel resistance value of the resistor 31 and the resistor 32. That is, in this case as well, the response of the reproduced signal punching means 104 becomes slow, so that the same effect as described in the embodiment of FIG. 4 can be obtained.

Furthermore, as a result of the switch 33 being opened, the output of the comparing means 101 is divided by the resistors 31 and 32 with reference to the constant voltage source and is applied to the feedback means 102. Comparison means 101
When the output is two values of VDD and ground potential, the signal input to the feedback means 102 is VDD and vc, that is, vc-VDD-R32/(R31+), as shown in FIG. 7(e).
R32)...Takes the binary value of (6). If the values of R31 and R32 are appropriately selected, it is possible to compensate for the decrease in the average value of the output of the comparing means 101 when the track open sound is detected as a no-signal portion, and as a result, as described in the embodiment of FIG. You can get the same effect as

As described above, according to this embodiment, the input resistance 12 of the feedback means 102, which is a determining factor of the response frequency, and the input resistance 12 of the comparison means 10
By connecting a parallel connection circuit of a resistor 32 and a switch 33 between the output side of the resistor 32 and the output side of the resistor 32, and pulling up the output side of the resistor 32 with the resistor 31, 5. To realize a more economical track-to-track detection device since it is not a buggy that can obtain the same effect as the embodiment shown in FIG. 4, and requires only one switch compared to the embodiment shown in FIG. 4. I can do it.

Effects of the Invention As is clear from the above explanation, the present invention passes a signal reproduced from a recording medium through a waveform shaping means, and uses the output of the waveform shaping means to drive a retrigger type single pulse generation means. It is possible to detect gaps between tracks with high reliability even when searching for tracks at high speed.

Furthermore, by configuring the waveform shaping means to include a comparison means, a feedback means, and a constant switching circuit, the feedback circuit determines the threshold at which the signal should be waveform-shaped, so that variations in read and reproduced signals due to differences in recording media Moreover, by simply changing the switch in the constant switching circuit, the circuit can be used for normal reproduction of signals on a track.

Furthermore, as illustrated in FIG. 9 above, a first resistor is inserted in series in front of the feedback means as a constant switching circuit,
If the feedback circuit side is pulled up to a constant voltage source by a second resistor, and both ends of the first resistor are opened and shorted, the above-mentioned effects can be achieved with a smaller number of configurations. I can do it.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional track-to-track detection device;
The figure is a signal waveform diagram to explain the operation, Figure 3 is a schematic diagram showing the relationship between the track and the reading position, Figure 4 is a basic block diagram of an embodiment of the present invention, and Figure 6 is the same as the same book. A signal waveform diagram that does not fully explain the operation of the embodiment of the invention, FIG. 6 is a main circuit diagram of a specific embodiment of the invention, and FIGS. 7 and 8 are waveforms for explaining the operation of the embodiment of the invention. 9 are essential circuit diagrams of still another embodiment of the present invention. 100...Waveform shaping means, 200...Single pulse generation means, 101...Comparison means, 102
...Feedback means, 103, 103'...Constant switching circuit, 104...Reproduction signal punching means, 3
1.32...Resistance 4.33...Switch. Name of agent: Patent attorney Toshio Nakao and 1 other person
3 Figure 4 Figure 47 ■

Claims (1)

[Claims] (1) A read and reproduced signal extracted in time series from a recording medium having a track formed by an array of binary signals with a limited maximum inversion interval is converted into a rectangular wave signal using a predetermined threshold. a retrigger type single pulse that is driven by the edge of the read and reproduced signal shaped by the waveform shaping means and that maintains the same potential for a longer time than the maximum edge interval of the shaped read and reproduced signal; Track-to-track detection device (2) characterized in that it is equipped with a generating means and detects the track-to-track by the output of the single pulse generating means.
The waveform shaping means shapes the read reproduction signal into a rectangular wave with a predetermined threshold value, and the feedback means substantially determines the threshold level so that the average value of the read reproduction signal waveform-shaped by the comparison means becomes a reference voltage. and a constant switching circuit for changing the response speed of the reproduction signal, number punching means and the reference voltage when searching for a target track. An inter-track detection device according to claim (1). (3) The constant switching circuit includes a first resistor connected in a signal path from the output side of the comparing means to the input side of the feedback means;
A second resistor connected between the output terminal of the first resistor and a constant voltage source, and a switch capable of opening and shorting both ends of the first resistor. An inter-track detection device according to claim (2).