JPH11339278A - Track count circuit for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a track count circuit for an optical disk such that can eliminate effects due to various noises generated in binarized signals and that can accurately count the number of tracks on which an optical pickup moved. SOLUTION: This circuit is equipped with a comparator 1 for forming a signal for which a tracking error signal or a mirror signal is binarized, a time constant converting part 3 which outputs time constant A in accordance with the pulse width of a track count pulse, a corrugated shaping part 2 for outputting the track count pulse in which the effects of a noise is eliminated from the binarized signal by performing the addition/subtraction of the time constants, and a tracking counter part 4 which calculates the number of moving tracks an optical pickup by counting the number of the track count pulses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track count circuit for an optical disk, and more particularly to an optical disk (CD, CD-
The present invention relates to a track count pulse shaping circuit in a track jump circuit of a driver (ROM, DVD, etc.).

[0002]

2. Description of the Related Art In order to access at a high speed a predetermined track of a disk on which storage tracks are formed spirally or circumferentially, an optical pickup (optical head) is moved in the radial direction of the disk and the number of tracks (tracks) traversed. (The number of traversing the concave / convex surface forming the pattern) is accessed by a track jump.

Usually, optical pickups include a, b, c,
The four sensors d are arranged in a matrix, and a mirror signal (MIRR signal) having a peak at the center of each of the concave and convex surfaces of the disk is detected from the output of (a + b + c + d) at the time of the track jump, and the output of (a + b) And (c
A tracking error signal (TE signal) having a peak at the boundary between the concave surface and the convex surface of the disk is detected from the difference from the output of + d). During playback, the concave surface (signal surface) of the given track
Is read by the output of (a + b + c + d).

[0004] Then, CD, CD-ROM or DV
The information on the moving distance and the moving speed of the optical pickup at the time of the track jump in the D servo is obtained from the pulse obtained by shaping the MIRR signal or the TE signal.

The outline will be described with reference to FIG.

FIG. 7A shows an MIR at the time of a track jump.
R signal, FIG. 7B shows a TE signal at the time of a track jump,
FIG. 7C shows a signal obtained by binarizing the MIRR signal by the comparator, and FIG. 7D shows a tracking error zero-cross signal (TEC signal) obtained by binarizing the TE signal by the comparator.

The number of tracks of the optical pickup is calculated by counting the number of track count pulses obtained from the number of the binarized signals by the tracking counter unit.

However, these signals include FIG.
As shown in (C) and (D), high frequency (short period) near zero cross (near rising and falling)
Noise NE is generated. Therefore, an error occurs in the count number of the moving track, which hinders recognition of the accurate movement of the optical pickup.

For this reason, a method of blocking high-frequency noise using a low-pass filter has conventionally been used. In the track jump operation, the optical pickup gradually accelerates from an initial speed of zero, then decelerates and stops at the target track, so that both the frequency of the binarized signal and the frequency of the noise generated there are during operation. Change. Therefore, in Japanese Patent Application Laid-Open No. 9-167354, a variable low-pass filter whose cut-off frequency changes according to the operating speed of the optical pickup in the radial direction is used, and the binarized TE signal is passed through this variable filter. A technique for removing noise has been disclosed.

[0010]

The prior art using a low-pass filter as described above has a problem as shown in FIG.

That is, when the noise NE is generated only near the zero cross of the TEC signal obtained by binarizing the TE signal, the noise NE component is removed by a low-pass filter having a cut-off pulse width of 100. As shown in B), a desired track count pulse signal is obtained, and correct counting can be performed.

However, as shown in FIG.
If a noise NC whose cycle is shorter than the cutoff pulse width 100 is generated after the TEC signal rises (or falls), the TEC signal itself is cut off by the low-pass filter, and FIG.
As shown in (C), since a track count pulse cannot be obtained, correct counting becomes impossible.

[0013]

According to the present invention, there is provided a comparator for forming a binary signal of a tracking error signal or a mirror signal (a tracking error zero-cross signal in the case of a tracking error signal), and a pulse width of a track count pulse. A time constant conversion unit that outputs a corresponding time constant A, and the effect of noise is removed from the binarized signal (tracking error zero-cross signal in the case of a tracking error signal) by adding and subtracting the time constant A. The track count circuit of the optical disc includes a waveform shaping section that outputs a track count pulse, and a tracking counter section that calculates the number of tracks moved by the optical pickup by counting the number of track count pulses. Here, the time constant A can be output according to the pulse width of the immediately preceding track count pulse.

The waveform shaping section performs addition and subtraction of the time constant A according to the polarity of noise included in the binarized signal (tracking error zero cross signal in the case of a tracking error signal) by a polarity control circuit. Instruct,
According to this instruction, the addition and subtraction of the time constant A are performed by the adder, and after a predetermined time has elapsed from the zero crossing point,
It is preferable that the circuit configuration is such that a track count pulse is set / reset according to the polarity of the binarized signal. In this case, the waveform shaping unit receives the first signal, the clock signal and the overflow / underflow detection signal from the adder.
An ND circuit, a second AND circuit for inputting an inverted signal of the binarized signal, a clock signal, and an overflow / underflow detection signal from the adder, and a set from the first and second AND circuits An RS latch circuit that receives a reset signal and outputs the track count pulse can be provided.

Further, the time constant conversion section detects an edge of the track count pulse signal, and after detection, outputs a latch pulse signal and a reset signal. A counter circuit that is cleared by the reset signal or the external reset signal from the unit, a latch circuit, and the time constant A from the count number data between edges of the tracking count pulse signal supplied from the latch circuit. And a time constant conversion table circuit. Here, the time constant conversion unit may include a selector circuit capable of externally setting the time constant A.

As described above, according to the present invention, the time constant is determined at any time according to the pulse width of the track count pulse, that is, according to the frequency of the track count pulse, and the time constant A is output. Addition (subtraction when the polarity is negative) is performed by changing the polarity of the constant A, and after the time corresponding to the noise margin elapses, the binarized signal,
Set track count pulse according to polarity of TEC
Since the circuit is configured to be reset, it is shaped into a track count pulse containing no noise, and enables accurate counting of the number of tracks moved by the optical pickup and detection of the moving speed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

1 to 6 show an embodiment of the present invention. In this embodiment, a tracking error signal (TE signal) is binarized by a comparator to form a tracking error zero-cross signal (TEC signal). Explain the case. However, the same applies when the mirror signal is binarized by a comparator.

FIG. 1 is a block diagram of the embodiment. In FIG. 1, a comparator 1, a waveform shaping unit 2, a time constant conversion unit 3, and a tracking counter unit 4 are provided.

Tracking error signal (TE signal) 11
Is binarized by the comparator 1 and supplied to the waveform shaping unit 2 as a tracking error zero cross signal (TEC signal) 12.

In the waveform shaping section 2, a time constant A is calculated according to the polarity of the TEC signal 12 by an 8-bit adder 203 shown in FIG.
By performing addition and subtraction at (−128 <sum <127), noise near the tracking error / zero cross is removed, and the track count pulse signal 13 is shaped. The time constant A (8 bits) (14) is supplied from the time constant converter 3.

The shaped track count pulse signal 1
3 is output to the tracking counter unit 4 and is used for counting the number of tracks of the optical pickup and detecting the moving speed.

Referring to FIG. 2, the waveform shaping section 2 of FIG. 1 is configured as follows. That is, the binarized tracking error zero cross signal (TEC signal) 12
Is input to the data port (D) of the D flip-flop circuit (DFF circuit) 201. Also, the DFF circuit 201
The clock signal (C) of FIG.

Therefore, the tracking error zero cross signal (TEC signal) 15 output from the output port (Q) of the DFF circuit 201 becomes the TEC signal 15 synchronized with the clock signal 20.

The polarity control circuit 202 has the time constant A (14) output from the time constant conversion circuit 3 and the TEC signal 1
5 has been entered.

The output signal 16 from the polarity control circuit 202 outputs a reverse polarity to the input 14 having the time constant A when the TEC signal 15 is "L", and outputs a positive polarity when the TEC signal 15 is "H". It is controlled to output as it is.

In the adder 203, the time constant A (14) and 1
The previous operation result signal 18 (sum18) is added. The calculation is executed for each cycle of the clock signal 20 and when the polarity of the time constant A (14) is inverted.

When the operation of the sum18 + (plus) time constant A or the operation of the sum18- (minus) time constant A overflows or underflows, the overflow / underflow detection signal 29 becomes active "H". In the adder 203, an overflow is a state in which the state in which the addition of 126 data has already been performed is further added, and an underflow is a state in which the state in which the subtraction of 127 data has already been performed is further subtracted. It is in a state to do.

A latch circuit 2 for outputting sum18
A feedback signal 17 and a latch pulse signal 19 of the detection result are input to 04. An AND circuit 205 is provided so that the latch pulse signal 19 is not activated when overflow / underflow is detected. The inverted signal of the clock signal 20 and the inverted signal of the overflow / underflow detection signal 29 are input.

Further, the output of the RS latch circuit 208 is
When the clock signal 20 is at “H” level and the overflow / underflow detection signal 29 is active,
Preset or reset. The switching between the preset and the reset is performed by the AND circuits 206 and 207, and is set when the TEC signal 15 is “H” and reset when the TEC signal 15 is “L”. That is, the AND circuit 206
The C signal 15, the clock signal 20, and the overflow / underflow detection signal 29 are inputted, and the output thereof is RS
The signal is input to the set port of the latch circuit 208. Also,
The inverted signal of the TEC signal 15, the clock signal 20, and the overflow / underflow detection signal 29 are input to the AND circuit 207, and the output thereof is supplied to the RS latch circuit 20.
8 is input to the reset port. Then, the output of the RS latch 208 is output as the track count pulse 13 to the track count unit 4 (FIG. 1).

Referring to FIG. 3, the time constant converter 3 shown in FIG.
Is configured as follows. That is, the track count pulse signal 13 is input to the timing generator 301.

The timing generation section 301 detects the edge of the track count pulse signal 13 and, after detection, outputs the latch pulse signal 22 and the counter reset pulse signal 21 in this order.

The counter circuit 302 outputs the clock signal 20
The reset signal 21 output from the timing generator 301 or the external reset signal 2
Cleared at 8.

The upper limit value of the counter circuit 302 is predetermined, and the counter circuit 302 stops counting at the upper limit value.

The data signal 23 is sent from the counter circuit 302 to the latch circuit 303, and the data signal 24 latched by the latch circuit 303 is supplied to the time constant conversion table circuit 304. The time constant conversion table circuit converts the count number between edges of the tracking count pulse signal 13 into a time constant. The time constant A (14) is a value satisfying the following equation.

255 (data width of addition notation 203 (FIG. 2)) / A (time constant) × T (cycle of clock signal 20) =
NM (Noise Margin) Here, the noise margin NM is, as shown in FIG.
It is an area (time domain) that covers an area (time domain) where it is expected that many noises (noise) n1, n2. It is appropriate that NM is set to about 1/4 cycle of the tracking count pulse 13. As shown in FIG. 4, a calculation is performed using a time constant A corresponding to the immediately preceding tracking pulse width 50, which is a
This is applied to the addition and subtraction of the next NM indicated by.

In the track jump operation, the optical pickup gradually accelerates from an initial speed of zero, decelerates to a target track, and stops. Therefore, the tracking pulse width gradually decreases from the start (frequency increases),
After the peak speed, the tracking pulse width gradually increases (frequency decreases).

Therefore, the area width (time width) of the NM gradually decreases from the start, and the area width (time width) gradually increases after passing the peak speed.

The data width of the adder used is constant.
Since the period of the clock signal is also constant, each NM
In order to perform the addition / subtraction operation in the area, it is necessary to reduce the time constant A as the tracking pulse width becomes longer, that is, as the NM area width becomes larger, so that more addition / subtraction is performed.

That is, the time constant A gradually increases from the start of the optical pickup, and gradually decreases after passing the peak speed.

Incidentally, the comparator 1 and the tracking counter section 4 in FIG. 1 have a conventional ordinary configuration, and a detailed description thereof will be omitted. Next, the operation of the present embodiment will be described with reference to FIGS.

The tracking error signal (TE signal) 11 shown in FIG. 4A is a sine wave from which the DC component has been cut. The TE signal 11 when the optical pickup is gradually accelerating is shown from the left to the center of the drawing, and the TE signal 11 when the optical pickup is gradually decelerating from the center to the right in the drawing.

The TE signal 11 is binarized by the comparator 1 and a tracking error zero-cross signal (TE
C signal).

FIG. 4B shows the TEC signal 15 after passing through the DFF circuit 201 of FIG. As shown in the figure, a spike-like noise is generated near the zero cross in the TEC signal 15 (or the TEC signal 12 before passing through the DFF circuit 201). That is, each N
M includes spike noises n1, n2, n3,...

In the present invention, the noise near the zero cross is removed by the waveform shaping circuit 2 to obtain the track count pulse signal 13 as shown in FIG.

Next, regarding the operation of the waveform shaping circuit 2, TE
The operation of removing noise when the C signal 15 (or the TEC signal 12) changes from L "to" H "will be described with reference to the timing chart of Fig. 5. That is, Fig. 5 shows one time domain NM of Fig. 4. 5A is an enlarged view of FIG. 5A and its vicinity, and FIG. 5A shows a tracking error signal (TE signal).
Noises n1 and n due to noise near zero crossing 11
5B shows a TEC signal 15 having 2, n3, n4, n5, and n6, and FIG.

FIG. 5C is a diagram in which the vertical dimension is the time constant A and the horizontal dimension is the clock signal 20.
Adder output signal 18 consisting of a plurality of steps having a cycle of
FIG. FIG. 5D shows the overflow / underflow detection signal 29, and FIG. 5E shows the track count pulse signal 13.

In FIG. 5, since the TEC signal 15 is "H" in the n1 area, the polarity control circuit 202 outputs the time constant A as it is with a positive polarity. Is added for each cycle of the clock signal 20.

Conversely, in the n2 region where the TEC signal 15 has changed to "L", the polarity control circuit 202 outputs the time constant A with a negative polarity, and the adder 203 outputs the sum8-
The calculation of (minus) A is repeated.

Similarly, in the n3, n5, and n7 regions, su
The operation of m8 + (plus) A is performed in the n4 and n6 areas by su
The calculation of m8- (minus) A is repeated.

The TEC signal 15 stabilizes at "H" while repeatedly changing "H" and "L" like n1 to n6.

That is, even when noise is present, since the "H" component is dominant at the time of the rise of the signal, "H"
To be stable. Similarly, at the time when the signal falls, the "L" component is dominant and stabilizes at "L" even if noise is present.

When the time corresponding to the noise margin (NM) has elapsed in the "H" area, the adder 203 overflows.

Then, at the level “H” of the clock signal 20 after the overflow / underflow detection signal 29 has changed to active “H”, the RS latch circuit 208 is set, and the track count pulse 13 becomes “H”. .

Similarly, when the TEC signal 15 changes from “H” to “L”, the adder 203 repeats subtraction and addition of the time constant A according to the polarity of the TEC signal 15.

After the “L” region of the TEC signal 15 has passed the noise margin (NM), the adder 203 underflows, and the overflow / underflow detection signal 2
At the level “H” of the clock signal 20 after the signal 9 changes to active “H”, the RS latch 208 is reset, and the output of the track count pulse 3 is inverted to “L”.

Also, if the noise NC is present after the output of the RS latch circuit 208 is once set to "H" and the TEC signal 15 falls to "L" due to this noise, NC 'in FIG. As shown in FIG.
The operation of sum8- (minus) A is executed in
The overflow signal 29 is inverted to inactive "L" while the clock 20 is at "L" level. RS latch 2
08 operates at the "H" level timing of the clock 20, so that the output of the RS latch circuit 208 is not reset by mistake. Conversely, after the output of the RS latch circuit 208 is once set to “L”,
Similarly, when there is noise in which the signal 15 becomes “H”,
It is not set by mistake. That is, the timing of the change of the overflow signal 29 and the timing of the set and reset of the RS latch 208 are shifted on the front and back of the clock 20. As a result, a predetermined track count pulse 13 is obtained as shown in FIG.

The time constant A is supplied from the time constant converter 3. When the external reset 28 is released, the counter circuit 302 starts free running. As long as the optical pickup does not start moving immediately after the external reset is released, the tracking error signal is stable in the “H” or “L” state, and the counter circuit 302 stops at the upper limit. Therefore, the movement of the optical pickup starts,
The minimum time constant is applied to the noise margin for the first two zero cross edges. From the third edge, a time constant corresponding to the pulse width of the tracking count pulse 13 is supplied to the waveform shaping unit 2. By repeating the above operation, the extraneous noise of the tracking error is completely removed, and the shaped track count pulse is supplied to the subsequent tracking count unit. As another embodiment of the present invention, the basic configuration is as described above. However, a selector circuit 305 is provided in the time constant converter 3 so that a time constant external input can be set so that the time constant can be externally set. 26, the external input time constant 26 and the internally formed time constant from the internal time constant conversion table can be selected by the select signal 27. The time constant at the start of the track jump can also be set. In addition, the time constant conversion table circuit
With the M configuration, the time constant conversion table can be changed, and the accuracy of noise removal can be improved.

Further, as an embodiment of the present invention, the shaping of a tracking error signal (TE signal) at the time of a tracking jump in an optical disk servo system or the like has been described. The mirror signal (MIRR signal) at the time of a tracking jump of the same system is also described. Similarly, waveform shaping is possible.

Since the mirror signal indicates “H” or “L” depending on the presence or absence of a pit on the disk, the number of moving tracks can be counted by counting the pulses, and the position of the pickup can be known. However, as in the case of the tracking error signal, noise may be added to the original waveform due to extraneous noise or scratches on the disk. As a result, accurate counting is not possible without shaping.

Therefore, in the above embodiment,
By exchanging the tracking error signal (TE signal) and the mirror signal (MIRR signal), the same effect as in the case of the waveform shaping of the tracking error signal in the embodiment can be obtained in the case of the mirror signal. Using the shaped waveform as a track count pulse, accurate positioning of the optical pickup can be performed.

[0062]

Advantages of the Invention Since the time constant is determined according to the pulse width of the track count pulse, even if the frequency of the tracking error signal changes, noise corresponding to the noise margin is reliably removed. 2. The adder 203 switches the addition and subtraction of the time constant A according to the polarity of the TEC signal 2, and thus also removes external noise immediately after the adder 203 overflows or underflows. 3. For the above reason, a tracking count pulse from which noise has been removed is generated, and the number of tracks moved by the optical pickup can be accurately counted.

4. Since the shaped track count pulse reproduces the original pulse width, the moving speed of the optical pickup can be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a waveform shaping unit according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a time constant conversion unit according to the embodiment of the present invention.

FIG. 4 is a waveform chart showing the operation of the embodiment of the present invention.

FIG. 5 is a waveform chart showing the operation of the embodiment of the present invention.

FIG. 6 is a waveform chart showing an operation in the present invention in comparison with FIG. 8 (prior art).

FIG. 7 is a diagram showing a conventional technique.

FIG. 8 is a waveform diagram showing a problem of the related art.

[Explanation of symbols]

Reference Signs List 1 comparator 2 waveform shaping unit 3 time constant conversion unit 4 tracking counter unit 11 tracking error signal 12 tracking error zero cross signal (TEC signal) 13 track count pulse signal 14 time constant A 15 tracking error zero cross signal (TEC signal) 16 polarity control circuit 17 Feedback signal of detection result 18 Previous operation result signal 19 Latch pulse signal 20 Clock signal 21 Reset signal 22 Latch pulse signal 23 Signal from counter circuit to latch circuit 24 Latch circuit to time constant conversion table circuit 25 Signal from the time constant conversion table circuit to the selector circuit 26 Time constant external input signal 27 Select signal 28 External reset signal 29 Overflow / underflow detection signal 201 D free Flop circuit 202 the polarity control circuit 203 the adder 204 the latch circuit 205 the AND circuit 206 the AND circuit 207 the AND circuit 208 RS latch circuit 301 timing generating unit 302 the counter circuit 303 latch circuit 304 at constant conversion table circuit 305 selector circuits

Claims (7)

[Claims] 1. A comparator for forming a signal obtained by binarizing a tracking error signal or a mirror signal, a time constant converter for outputting a time constant according to a pulse width of a track count pulse, and an addition and subtraction of the time constant. A waveform shaping unit that outputs a track count pulse from which the influence of noise has been removed from the binarized signal, and a tracking counter unit that calculates the number of moving tracks of the optical pickup by counting the number of track count pulses. A track count circuit for an optical disk, comprising: 2. A track count circuit for an optical disk according to claim 1, wherein a tracking error zero-cross signal is formed by binarizing the tracking error signal. 3. The track count circuit for an optical disk according to claim 1, wherein said time constant is output in accordance with the pulse width of the immediately preceding track count pulse. 4. The waveform shaping section instructs addition and subtraction of the time constant by a polarity control circuit in accordance with the polarity of noise included in the binarized signal. 2. The circuit configuration according to claim 1, wherein addition and subtraction are performed, and after a predetermined time has elapsed from a zero crossing point, a track count pulse is set / reset according to the polarity of the binarized signal. Track count circuit of optical disk. 5. The waveform shaping section includes a first AND circuit that inputs the binarized signal, a clock signal, and an overflow / underflow detection signal from the adder, and inverts the binarized signal. A second AND circuit for inputting a signal, a clock signal and an overflow / underflow detection signal from the adder, and a set / reset signal from the first and second AND circuits for outputting the track count pulse 5. The track count circuit of an optical disk according to claim 4, further comprising an RS latch circuit that performs the operation. 6. The time constant conversion section detects an edge of the track count pulse signal, and after detection, outputs a latch pulse signal and a reset signal. A counter circuit cleared by the reset signal or the external reset signal from the unit, a latch circuit,
2. The optical disk track according to claim 1, further comprising a time constant conversion table circuit for generating a time constant from data of a count number between edges of the tracking count pulse signal supplied from the latch circuit. Count circuit. 7. The track count circuit for an optical disk according to claim 6, wherein said time constant conversion unit has a selector circuit capable of setting a time constant from outside.