JP2763937B2 - Sector mark detection circuit of optical disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a sector mark detection circuit of an optical disk device that detects a sector mark of an optical disk preformatted for sector synchronization, and to prevent erroneous detection of a sector mark. Focusing on the fact that the level of DCSUM from the light receiver provided on the head decreases in the preformat area, this DCSUM
A detection window that is turned on near the changing point of decreasing the number of pixels is set, and only the correct sector mark detection pulse is obtained through this setting window.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sector mark detection circuit of an optical disk device that performs sector synchronization by detecting a preformatted sector mark.

2. Description of the Related Art An optical disk device has a large storage capacity because a track interval can be set on the order of several microns, and has recently attracted attention as a large-capacity storage device such as a computer system.

A write-once optical disc is designed to simultaneously create a sector mark for obtaining a sector synchronization signal and an ID code indicating a sector address, together with a pre-groove, which is a guide groove for recording data at the time of disc manufacture, and has already formatted the area. In this sense, it is called a preformat area.

In order to record or reproduce data, a target sector is searched based on address information. At this time, a reproduction signal of a sector mark formed in a preformat area is determined and a sector mark detection pulse is output. A sector mark detection circuit is provided.

However, in general, sector mark detection performance is low. In particular, sector marks are often erroneously detected due to a medium defect or the like in an unrecorded portion of an optical disk, and accurate sector mark detection performance that does not cause erroneous detection. Is required.

[Prior Art] FIG. 5 shows a pit structure of a sector mark preformatted on an ISO standard 5-inch optical disc.
The read signal of the sector mark shown in FIG. 6 can be obtained from the light receiving output of the beam return light when the sector mark is traced.

FIG. 7 shows an example of a conventional sector mark detection circuit.
The pit interval τ determined by the minimum pit size and the rotation speed is defined as one unit, and two pulse width detectors, 5τ detector 26 and 3τ detector 28, are provided. The signal is output to the circuit 38. Meanwhile, 3
τ detection pulse is 24τ delay 32, 14τ delay 34 and 8
After being delayed by each of the τ delays, it is output to the majority circuit.

That is, when the read signal of the sector mark is correctly obtained, the respective detection pulses at times t1 to t4 in FIG. 5 are given to the majority circuit 28 at time t5 with the delay shown in FIG. If three or more pulses are obtained, a sector mark detection pulse is output.

[Problems to be Solved by the Invention] However, in the conventional sector mark detection circuit shown in FIG. 7, the detection performance of the sector mark is low, and particularly, the first sector search is performed in the unrecorded portion of the optical disk. At that time,
There is a problem that a sector mark is erroneously detected due to a medium defect or the like.

Once the controller of the optical disk device has detected the sector mark, the sector mark detection window can be set at a position where the detection of the corresponding sector mark is scheduled by measuring the time from the detected sector mark, Erroneous detection of a sector mark due to a medium defect, noise, or the like can be prevented.

However, a sector mark detection operation called a pre-sector mark search is performed after the track servo is turned on or at the end of the track jump. At the time of this pre-sector mark search, since the detection window is opened and is not set, the possibility of erroneous detection increases.

Further, the determination of whether or not the sector mark is erroneously detected is performed by reading IDs for several sectors and determining that the ID is erroneous when the ID cannot be read, and performing the retry operation from the pre-sector mark search when determining the erroneous detection. Performance decreases.

In order to prevent erroneous detection of a sector mark, it is conceivable to increase the margin of the majority circuit 38 shown in FIG. For example, in the majority circuit 38, four out of five detection pulses
Strictly, a detection pulse of a sector mark is output when one is obtained. However, when the margin for detecting the sector mark is reduced, the detection performance of the sector mark becomes extremely low, so that there is a problem that the improvement of the detection performance and the prevention of the erroneous detection cannot be achieved at the same time.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has as its object to provide a sector mark detection circuit of an optical disk device that can reliably prevent erroneous detection of a sector mark.

[Means for Solving the Problems] FIG. 1 is an explanatory view of the principle of the present invention.

First, the present invention provides a medium 10 in which sector marks SM are pre-formatted, and a sector mark determination circuit 14 which determines a reproduction signal of a sector mark included in a read signal of the medium 10 by the optical head 12 and outputs a sector mark detection pulse. And a sector mark detection circuit of an optical disk device having the following.

According to the present invention, the sector mark detection circuit of such an optical disk device is used for a predetermined period from a change point at which the DC sum signal DCSUM obtained by adding all the light reception outputs of the light receiver 16 provided in the optical head 12 decreases. During this period, a detection window setting circuit 20 that opens the gate 18 to allow the passage of the sector mark detection signal is provided.

Here, the detection window setting circuit 20 outputs the DC sum signal DC
A low-pass filter 22 for slowing down the change in SUM,
The output of the adder 24 that adds a predetermined bias voltage + V to the DC sum signal DCSUM is compared with the outputs of the low-pass filter 22 and the adder 24. The window setting pulse is applied to the gate 18 while the output of the low-pass filter exceeds the output of the adder. And a comparator 26 that outputs

[Operation] According to the sector mark detection circuit of the present invention having such a configuration, based on the decreasing change of the DCSUM obtained from the return light from the sector mark preformatted on the optical disk, The reflected light is attenuated at the pits when it reaches the sector mark due to DCSU.
Since the detection window is set based on the decrease in M, even in the first sector mark search of the unrecorded part, the sector mark can be detected accurately without causing false detection, and the detection performance is improved. Thus, a high-speed apparatus that requires less processing time for address confirmation performed after a track jump can be realized.

[Embodiment] Fig. 2 is an embodiment configuration diagram showing one embodiment of the present invention.

In FIG. 2, an optical disk 10 is rotated at a constant speed of, for example, 3600 rpm by a spindle motor 25. Reference numeral 12 denotes an optical head, which is a VC in the radial direction of the optical disk 10.
It is movably provided by an M positioner 44, and a light beam can be moved in a direction traversing the track by a track actuator mounted in the optical head 12. Further, the position of the track actuator provided in the optical head 12 is detected by a position sensor.

Reference numeral 40 denotes a track servo circuit, which receives a track servo-on control from the MPU 100, detects a tracking error signal TES based on the output of a four-divided photodetector provided on the optical head 12 and receives return light, and performs phase compensation. After doing
The track actuator is controlled by the current drive of the tracking coil so that the tracking error signal TES is minimized.

Reference numeral 42 denotes a positioner servo circuit, which receives the positioner servo-on control from the MPU 100 and controls the VCM positioner 4 so that the direction position signal PLOS obtained from the position sensor of the track actuator provided on the optical head 12 is minimized.
Drive 4

Of course, the optical head 12 is provided with a focus actuator, and the focusing servo is controlled by an actuator servo circuit (not shown) so that a beam spot is formed on a track of the optical disk.

Further, the received light output from the four-divided light receiver provided in the optical head 12 is supplied to a read circuit 46, which demodulates read data from a high-frequency reproduction signal RFS based on the received light signal, and sends the demodulated data to a higher-level device via the MPU 100 Sends read data.

The output of the read circuit 46 is input to the sector mark determination circuit 14, and if the optical disk 10 is included in the read signal and preformatted, for example, an ISO standard 5-inch disk, the sector mark shown in FIG. And outputs a sector mark detection pulse Ps by determining the sector mark reproduction signal obtained from the pit structure. As the sector mark judgment circuit 14, the conventional sector mark judgment circuit shown in FIG. 7 is used as it is.

Reference numeral 20 denotes a detection window setting circuit newly provided in the present invention, and includes a low-pass filter 22, an adder 24, and a comparator 26. To the detection window setting circuit 20, a DC signal, which is the sum of all the light-receiving outputs of the four-divided photodetectors provided in the optical head 12, that is, the DCSUM signal is input from the track servo circuit 40, and the low-pass filter 22 outputs the DCSUM signal. The rising and falling are made gentle and given to the plus input terminal of the comparator 26. The DCSUM signal is added with a predetermined bias voltage + V by the adder 24, and is given to the minus input terminal of the comparator 26 as (DCSUM + V).

The detection window setting circuit 20 outputs the DCSUM signal to the optical disc 10
Attention is paid to the fact that the sector mark SM is formed at the beginning of the preformat portion during the preformat portion, and the sector mark SM is formed at the beginning of the preformat portion. A window pulse Pw1 having a logic level 1 over the output period of the reproduction signal is generated.

The window pulse Pw1 of the detection window setting circuit 20 is input to one of the AND gates 70, and the other of the
From 0, a pre-sector mark window control signal S1 is given. That is, the MPU 100 sets the pre-sector mark window control signal S1 to 1 at the time of the pre-sector search operation performed after the track jump, sets the AND gate 70 to the allowable state, and outputs the window pulse Pw1 from the detection window setting circuit 20.

The output of the AND gate 70 is input to the OR gate 72, and the other of the OR gate 72 is supplied with the sector mark window control signal Pw2 from the MPU 100. This sector mark window control signal S2 is used for sector mark detection after the first sector mark detection is performed. That is, if the first sector mark can be detected, the position of the sector to be accessed indicates the elapsed time from the ID part following the detected sector mark by the MPU 100.
Can be predicted by measuring with the interpolation timer 102 provided in the window, and when the measured sector mark detection position is reached, the sector timer control signal S2 is output to the OR gate 72 under the control of the interpolation timer 102 to set the window. I can do it.

The output of the OR gate 72 is input to one of the AND gates 18,
The other side receives a sector mark detection pulse Ps from the sector mark determination circuit 14. AND gate 18 is OR gate 7
While the wind pulse Pw1 or Pw2 is obtained from 2,
In an allowable state, that is, when the gate is opened, the sector mark detection pulse Ps output from the sector mark determination circuit 14 while the gate is open is output to the MPU 100 as a valid detection pulse.

 FIG. 3 is a diagram showing an embodiment of an optical head according to the present invention.

In FIG. 3, a semiconductor laser 50 is provided in the optical head 12.
Is provided, and the elliptical diffused light from the semiconductor laser 50 is converted by the collimator lens 52 into a circular parallel beam. The parallel beam from the collimator lens 52 passes through the polarizing beam splitter 54, the λ / 4 plate 56, and the objective lens 58 to form a small beam spot on the optical disk 10. The polarizing beam splitter 54 is a combination of two prisms, and allows the P-polarized light to pass through as it is, while the S-polarized light is reflected at right angles. The λ / 4 plate converts the incident linearly polarized light into circularly polarized light, and converts the linearly polarized light into circularly polarized light. The reflected light of the beam spot formed on the optical disk 10 is reflected by the polarizing beam splitter 54 in a right angle direction, and is formed on the four-divided light receiver 16 by the condenser lens 60.

The four-divided light receiver 16 has four light-receiving portions A, B, C, and D as shown on the left side. The zero-order diffracted light reflected by the track guide groove of the optical disc 10 and the temporary diffracted light are superimposed. A light receiving output corresponding to the light intensity pattern of the portion is generated. The track servo circuit 40
Can be used to detect the tracking error signal TES. Tracking error signal TES is (A + D)
− (B + C) can be detected. Also, the focus error signal FES can be detected from the output of the four-segment light receiver 16. For example, in the case of the astigmatism method, FES = (A + B)-
It can be detected as (C + D). Further, by calculating the sum (A + B + C + D) of the light receiving outputs of the four-divided light receiver 16, the second
The DCSUM signal used in the detection window setting circuit 20 shown in the figure can be obtained.

The objective lens 58 provided on the optical head 12 is moved by a tracking coil 64 in a direction crossing the tracks of the optical disk 10 and is moved by a focus coil 66 in the axial direction. That is, the tracking coil 64 is driven by the output of the track servo circuit 40 shown in FIG. 2, while the focus coil 66 is driven by a focus servo circuit (not shown). Further, the position of the objective lens 58 by the tracking coil 64 is detected by the position sensor 68. As the position sensor 68, an optical position sensor having a light emitting element, a slit plate, and a two-divided light receiver is used. At a neutral position of the track actuator, zero, for example, a plus direction on the inner side, and a minus direction on the outer side. The linearly increasing direction position signal PLOS is detected and used by the positioner servo circuit 42 shown in FIG.

Next, the sector mark detecting operation of the present invention will be described with reference to FIG.

Now, assume that the MPU 100 ends the track jump and shifts to the fine control for turning on the track servo circuit 40, and sets the pre-sector mark window control signal S1 to S1 = 1 to detect the first sector mark in the unrecorded area. I do.

DCSUM obtained from the track servo circuit 40 in this state
The signal includes a sector mark SM serving as a pre-format part and
The signal level decreases stepwise in the ID section.

Therefore, in the detection window setting circuit 20, the adder 24 adds a predetermined bias voltage + V to the DCSUM signal (DCSUUM signal).
M + V) is input to the negative input terminal of the comparator 26, and the low-pass filter output of the DCSUM signal shown by the broken line in FIG. 4 that has passed through the low-pass filter 22 is input to the positive input terminal of the comparator 26.

Therefore, when the light beam reaches the sector mark SM at time t1, the output of the adder 24 indicated by the solid line, that is, (DCSUM + V)
The signal suddenly falls and the low-pass filter
The DCSUM signal passing through 22 gradually decreases as shown by the broken line. Therefore, from time t1 to time t2,
The output of the comparator 26 becomes 1 to generate a window pulse Pw1.

At this time, since the AND gate 70 is in an allowable state by the setting of the pre-sector mark window control signal S1 from the MPU 100, the window pulse Pw1 from the comparator 26
0, further applied to the AND gate 18 via the OR gate 72,
The D-gate 18 sets a sector mark detection window.

However, with respect to the sector mark between times t1 and t2, the sector mark determination circuit 14 cannot detect the sector mark, and the sector mark detection pulse is not obtained.

After passing the preformat portion at time t3, the DCSUM signal rises again and falls again at the preformat portion at the next time t4. In the same manner, for the sector mark from time t4 to time t5, the comparator 26
Pw1 is generated. At this time, if the sector mark detection pulse Ps is normally output from the sector mark determination circuit 14,
A sector mark detection pulse is supplied to the MPU 100 from the window pulse Pw1 through the AND gate 18 in an allowable state. MP
When U100 receives a sector mark detection pulse from the AND gate 18 in the pre-sector mark search state, the U100 resets the pre-sector mark window control signal S1 for the AND gate 70 to 0, and uses the sector mark window pulse Pw2 from the built-in interpolation timer 102. Switch to window setting.

In the case of FIG. 4, the sector mark determination circuit 14 generates an erroneous sector mark detection pulse due to a medium defect or the like between the first sector mark and the next sector mark. Since the window pulse Pw1 is not given, the erroneous detection of the sector mark detection pulse to the MPU 100 is prevented.

[Effects of the Invention] As described above, according to the present invention, a sector mark with high detection performance can be detected without changing the conventional margin for detecting a sector mark. In addition, the detection performance is improved to determine whether the sector mark detection pulse obtained by the pre-sector search after the track jump is erroneously detected, that is, whether the ID portion for a plurality of sectors, that is, the sector address can be read. Confirmation is not required, and the device performance can be improved at the same time as the reliability of sector mark detection is improved.

[Brief description of the drawings]

 FIG. 1 is a diagram illustrating the principle of the present invention; FIG. 2 is a diagram illustrating the configuration of an embodiment of the present invention; FIG. 3 is a diagram illustrating the configuration of an optical head according to the present invention; FIG. 5 is an explanatory diagram of a pit structure of a sector mark; FIG. 6 is an explanatory diagram of a read signal of a sector mark; FIG. 7 is a configuration diagram of a conventional circuit. In the figure, 10: medium (optical disk) 12: optical head 14: sector mark judgment circuit 16: quadrant photodetector 18: gate 20: detection window setting circuit 22: low-pass filter (LPF) 24: adder 26: comparator 40 : Track servo circuit 42: Positioner servo circuit 44: VCM positioner 46: Lead circuit 50: Semiconductor laser 52: Collimator lens 54: Polarizing beam splitter 56: λ / plate 58: Objective lens 60: Condenser lens 64: Tracking coil 66: Focus coil 68: Position sensor 70: AND gate 72: OR gate 100: MPU 102: Interpolation timer

Claims (2)

(57) [Claims] 1. A medium (10) in which a sector mark (SM) is pre-formatted; and a sector mark reproduction signal included in a read signal of the medium (10) by an optical head (12) is determined to determine a sector mark detection pulse. And a sector mark determining circuit (14) for outputting an optical head (12). The sector mark detecting circuit (14) provided by adding all the light receiving outputs of a light receiver (16) provided in an optical head (12). An optical disk having a detection window setting circuit (20) for opening a gate (18) so as to allow passage of the sector mark detection signal for a predetermined period from a change point at which a DC sum signal (DCSUM) decreases; The device's sector mark detection circuit. 2. The detection window setting means (20) comprises: a low-pass filter (22) for gradually decreasing a change in the DC sum signal (DCSUM); and a predetermined bias voltage (+) to the DC sum signal (DCSUM).
An adder (24) for adding V); comparing the outputs of the low-pass filter (22) and the adder (24), and setting a window on the gate (18) while the low-pass filter output exceeds the adder output. 2. The circuit according to claim 1, further comprising: a comparator for outputting a pulse.