JP2706345B2 - Optical disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive for recording / reproducing information on / from an information recording medium.

[Conventional technology]

2. Description of the Related Art In recent years, an optical disk, which is a recording medium having a large recording capacity, has been attracting attention due to a rapid increase in information processing amount in an information processing system. As a conventional servo system of an optical disk drive, there are a continuous groove system, a sampled servo system, and the like.

FIG. 4 is a block diagram showing a configuration of a conventional optical disk drive device. In FIG. 1, an optical head 1 is constituted by an optical system such as a semiconductor laser, a lens, a mirror, a photodiode for converting reflected light into light and outputting the same, and an actuator for moving the position of a movable lens. The laser drive unit 2 drives the laser of the optical head 1 with a control signal from the laser control unit 3. The optical head 1 emits a light beam to an optical disk 5 that is driven to rotate by a motor 4, receives reflected light from the optical disk 5, and splits the light by a detector (not shown). The divided reflected light is given to the photodiodes of the focus servo system and the tracking servo system, respectively. The photodiode of the tracking servo system divides the reflected light into two according to the detection position,
The detection signal is given to the head amplifier 6. The head amplifier 6 amplifies the two divided detection signals,
Give to. The addition / subtraction circuit 7 adds and subtracts the two divided detection signals, and the subtracted signal is supplied to a demodulation system (not shown) as a magneto-optical information signal. The added signal is supplied to the servo drive unit 8 as an Rf sum signal.
The servo drive unit 8 extracts a clock signal from the Rf sum signal,
A tracking control signal is formed by locking using a PLL circuit, and is provided to the optical head 1. The optical head 1 moves the movable lens according to the tracking control signal,
Tracking control is being performed.

The optical head 1 has a photodiode of a focus servo system that receives the reflected light split by the detector and supplies a focus error signal to the head amplifier 9. Head amplifier 9 differentially amplifies the signal, and amplifier 10
, A focus control signal is given to the optical head 1.
The optical head 1 performs a focus control by moving a lens in accordance with a focus control signal. This head amplifier 9
The amplifier 10 corrects the vertical movement of the optical disk 3 due to warpage or surface deflection, thereby forming a focus drive / control unit 11 for always focusing the light beam on the position of the recording surface of the optical disk 5.

FIG. 5 (a) is a diagram showing the shape and position of prepits on two conventional sampled servo optical disks, and FIG. 5 (b) is measured by a conventional optical disk drive.
It is a figure showing an Rf sum signal. As shown in FIG.
The center lines of the tracks of the optical disks 21 and 22 are set as center lines A and B, respectively. Here, a servo area 23 for detecting a tracking error signal and a data area 24 for reading and writing data are completely separated, and each of them is formed alternately on a track. The feature of the sampled servo method is that the wobble pits 25,
A large number of pre-pits are pre-formatted at predetermined intervals on a track or in the vicinity thereof at a predetermined interval or two types of pre-pits, ie, clock pits 26 and clock pits 27 and 28 for detecting a clock signal necessary for detecting a wobble pit. In the optical disc of the sampled servo system, the circumferential positions of the wobble pits 25 and 26 and the clock pits 27 and 28 are defined, but the shape and the deviation width of the position from the center of the track are as follows.
It is not specified at all and varies from manufacturer to manufacturer. In the servo area 23, the clock pits 27 and 28 are extracted and used as a clock signal, a wobble pit signal is extracted at the timing of the clock signal, and a tracking error signal is detected from the amplitude deviation.

In the conventional optical disk drive, clock pit 2
In order to synchronize the tracking error signal, recording / reproduction timing signal, address / track number read signal, etc. with the 7,28 clock signals, the clock pits can be accurately extracted when the optical disk is inserted into the optical disk drive. It becomes important.

In FIG. 5B, the curve C changes in response to the wobble pit 25 and the clock pit 27 of the optical disc 21.
Rf sum signal. Similarly, a curve D indicates an Rf sum signal that changes corresponding to the wobble pit 26 and the clock pit 28 of the optical disc 22. Thus, the amplitude of the Rf sum signal varies depending on the shape and position of the prepit.

FIG. 6 is a diagram showing a jitter of a clock signal detected by a conventional optical disk drive device measured by a time interval analyzer. In this figure, curves E and F indicate the number of clock signals detected from the optical discs 21 and 22 in FIG. 5 (a) and the number of clock signals of that period, respectively. As is clear from this figure, a clock signal detection error occurs on the optical disk 21 where the amplitude of the Rf sum signal is small. For example, certain optical discs 21 and 2
The jitters L ₁ and L ₂ of ₂ are 200 nsec and 100 nse, respectively, when the drive is turned on.
c. Note jitter is the width of the fluctuation in the time axis of the clock signal when measured 10 ^6.

[Problems to be solved by the invention]

In such a conventional optical disk drive, even when the optical disk is inserted into the optical disk drive, the focus is optimally adjusted in the data area as described above. Therefore, when pre-pit shapes and positions such as wobble pits and clock pits are different depending on the optical disk, a clock signal is erroneously extracted, the amplitude of the Rf sum signal cannot be sufficiently obtained, and servo is not applied. .

The present invention has been made in view of such a problem of the conventional optical disk drive device, and a stable servo can be applied when the optical disk is inserted into the optical disk drive device regardless of the shape and position of the prepit of the optical disk. Another object of the present invention is to improve the S / N ratio at the time of reproducing a signal recorded at least equal to that of a conventional optical disk drive device.

[Means for solving the problem]

The invention according to claim 1 of the present application is an optical disk drive device for recording / reproducing information by irradiating a light beam to an optical disk in which a number of prepits are preformatted in advance at tracks and in the vicinity thereof at regular intervals. An optical head having an optical system and a drive system that irradiates an optical disk with a light beam and divides reflected light into two according to the detection position of a light receiving element and outputs it as a detection signal, and a PLL circuit, and the amount of light received by the optical head A servo drive unit that extracts a clock signal from the sum signal of the above and outputs a PLL clock signal;
A focus control signal is formed based on the two divided detection signals from the optical head, and a focus drive / control unit that outputs the focus control signal to the optical head and an offset voltage that changes the focus position when the optical disk is inserted into the optical disk drive are added. And an offset voltage generator for outputting a focus control signal to the optical head and stopping the offset by a PLL clock signal from the servo driver after the servo is stabilized.

The invention according to claim 2 of the present application is characterized in that the offset voltage generator sets the focus offset level at which the amplitude modulation received from the prepits formed on the optical disk when the optical disk is inserted into the optical disk drive device is maximized. It is assumed that.

The invention according to claim 3 of the present application is characterized in that the control system of the optical disk is a sampled servo system.

The invention according to claim 4 of the present application is characterized in that the pre-pit is a clock pit.

[Action]

According to the present invention having such features, when the optical disk is inserted into the optical disk drive, the offset voltage generating unit adds the offset voltage for changing the focus position to the output from the focus drive / control unit, and controls the focus control signal. To the optical head. After the servo is stabilized, the servo driver extracts the clock signal from the sum signal,
The PLL lock signal is output to the offset voltage generator to stop the offset. The focus drive / control unit outputs a focus control signal to the optical head.

〔Example〕

An embodiment of the optical disk drive of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an optical disk drive device according to the present embodiment. The same parts as those in the above-described conventional example are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 1, the optical head 1 includes an optical system and an actuator. The laser driver 2 drives the laser of the optical head 1 based on the output from the laser controller 3. The optical head 1 irradiates the optical disk 5 with a light beam, receives the reflected light, divides the reflected light with a detector, and receives the light with a photodiode of a focus servo system and a photodiode of a tracking servo system, respectively. The photodiode of the tracking servo system divides the reflected light into two according to the detection position, and supplies the detection signal to the addition / subtraction circuit 7 via the head amplifier 6. The addition / subtraction circuit 7 converts the magneto-optical information signal and the Rf sum signal into a demodulation system and a servo drive unit, respectively.
Giving 31 is the same as in the above-described conventional example. The servo drive unit 31 extracts a clock signal from the Rf sum signal, forms a tracking control signal by locking using a PLL circuit, and supplies the tracking control signal to the optical head 1. Servo drive 31
Supplies a PLL lock signal to the offset voltage generator 32 after the servo is stabilized.

The photodiode of the focus servo system divides the reflected light into two parts according to the detection position, and supplies the detection signal to the head amplifier 9. The head amplifier 9 differentially amplifies the two divided detection signals and supplies the amplified signal to the amplifier 10, and supplies the amplified output to the optical head 1 as a focus control signal, as in the above-described conventional example. Here, the head amplifier 9 and the amplifier 10 constitute a focus drive / control unit 11 as in the conventional example.

In the present embodiment, the Rf sum signal is supplied to the offset voltage generator 32.
Is provided to the integrating circuit 33. The integration circuit 33 is an addition / subtraction circuit 7
The Rf sum signal given by the above is integrated, and the output is given to the A / D conversion circuit. The A / D conversion circuit 34 performs A / D conversion of an input from the integration circuit 33 and provides an output to the memory unit 35.
The signal stored in the memory unit 35 is transmitted to the microcomputer 36
, And calculates the offset voltage at which the Rf sum signal becomes maximum, and outputs the calculated offset voltage to the offset voltage generation circuit 37. The offset voltage generation circuit 37 is a microcomputer
Rf by sequentially changing the offset voltage according to the command from 36
The offset voltage at which the sum signal becomes maximum is supplied to the adder 39 via the switch 38. The switch 38 is the servo drive unit 31
The contact is opened by the PLL lock signal from the controller and closed when the PLL is unlocked. The adder 39 adds an offset voltage to a focus control signal output from the focus drive / control unit 11 and supplies the result to the optical head 1 as a focus control signal.

Next, the operation of the optical disk drive device according to the present embodiment will be described. First, when the optical disk 5 is inserted, the motor 4 rotates, and a light beam is applied to the recording surface to perform focus servo. When the optical disk 5 is inserted into the optical disk drive, Rf output from the addition / subtraction circuit 7
Since the amplitude of the sum signal cannot be sufficiently obtained, the servo drive unit 31 cannot lock the PLL circuit. At the time of unlocking, the PLL lock signal is not output to the switch 38, and the switch 38 is in the closed state. At this time, the integration circuit 33 integrates the Rf sum signal, performs an A / D conversion on the integrated output, and stores the result in the memory unit 35. The microcomputer 36 outputs a command for sequentially changing the offset voltage to the offset voltage generation circuit 37, whereby the offset voltage is sequentially changed, and the offset voltage at which the Rf sum signal input to the integration circuit 33 becomes the maximum level is set. You. The offset voltage generating circuit 37 outputs the set offset voltage to the adder 39 via the switch 38 in accordance with a command from the microcomputer 36. The adder 39 adds an offset voltage to the output from the focus drive / control unit 11 and outputs the result to the optical head 1 as a focus control signal. When the servo is stabilized, the servo drive unit 31 completely extracts the clock signal from the maximum level Rf sum signal. Then, the PLL circuit is locked, and the tracking control signal is given to the optical head 1. PLL at the same time
The switch 38 is released by the lock signal to stop the focus offset. At the time of the PLL lock, the light beam is focused on the optimum focus position in the data area, and the S / N ratio of the reproduction signal is maximized.

FIG. 2A is a diagram showing the shape and position of prepits using the sampled servo type optical disc of the present embodiment,
FIG. 2 (b) is a diagram showing signals subjected to amplitude modulation from the respective pre-pits. As shown in FIG. 2 (b), curves G and H are a wobble pit signal and a clock pit signal amplitude-modulated by the wobble pit and the clock pit of the optical disks 21 and 22, respectively. As can be seen from comparison with FIG. 5, the amplitudes of the Rf sum signals of the optical discs 21 and 22 are substantially at the same level.

FIG. 3 is a diagram showing the jitter of the clock signal detected by the optical disk drive of this embodiment using the same time interval analyzer as that of the conventional example. Jitter L ₃ of the clock signal the optical disk 21 together 1
0 was ^six measured and 50nsec.

In the optical disk drive device configured as described above,
When an optical disk is inserted into an optical disk drive
Focus servo is performed so that the Rf sum signal is maximized. The amplitude of the clock pit signal and the wobble pit signal is kept almost constant regardless of the shape and position of the clock pit and the wobble pit to reduce the jitter of the clock signal. It can be reduced to less than half.

〔The invention's effect〕

As described above in detail, according to the present invention, the focus position is changed when the optical disk is inserted into the optical disk drive device, and the focus control signal is added by adding an offset voltage that maximizes the amplitude of the amplitude modulation received from the pre-pit. By doing so, the clock signal can be easily extracted.
Therefore, even when different optical disks are loaded into the optical disk drive, stable servo can be applied. In addition, since the focus position is optimal for the data area at the time of recording / reproducing, an effect of improving the S / N ratio at the time of reproducing the recorded signal can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an optical disk drive device according to one embodiment of the present invention, FIG. 2 (a) is a diagram showing the shape and position of prepits according to this embodiment, and FIG. FIG. 3 is a diagram showing a corresponding Rf sum signal, FIG. 3 is a diagram showing jitter of a clock signal according to the present embodiment, FIG. 4 is a block diagram schematically showing a conventional optical disk drive device, and FIG. Diagram showing shape and position of pre-pit, FIG.
FIG. 6B shows a corresponding Rf sum signal, and FIG. 6 shows a conventional clock signal jitter. 1 optical head, 2 laser drive unit, 3 laser control unit, 6, 9 head amplifier, 7 addition / subtraction circuit, 10
...... Amplifier, 11 Focus drive / control unit, 31 Servo drive unit, 32 Offset voltage generation unit, 33 Integration circuit, 34 A / D conversion circuit, 35 Memory unit, 36 …… Microcomputer, 37 …… Offset voltage generation circuit,
38 ... Switch, 39 ... Adder.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-94033 (JP, A) JP-A-1-264634 (JP, A) JP-A-2-87330 (JP, A)

Claims (4)

(57) [Claims] 1. An optical disk drive device for recording and reproducing information by irradiating a light beam to an optical disk in which a number of prepits are pre-formatted on a track and its vicinity at predetermined intervals, and records / reproduces information. An optical head having an optical system and a drive system for irradiating the light beam and dividing the reflected light into two by the detection position of the light receiving element and outputting the signal as a detection signal; and a PLL circuit, and the amount of light received by the optical head is reduced. A servo drive unit that extracts a clock signal from the sum signal and outputs a PLL lock signal; and a focus drive / control unit that forms a focus control signal based on the two divided detection signals from the optical head and outputs the focus control signal to the optical head. And applying an offset voltage for changing a focus position when the optical disc is inserted into an optical disc drive. Output to the optical head as a focus control signal,
An optical disk drive device comprising: an offset voltage generation unit that stops an offset by a PLL lock signal from the servo drive unit after the servo is stabilized. 2. An offset voltage generator for setting a focus offset level at which the amplitude modulation received from a prepit formed on the optical disk when the optical disk is loaded into an optical disk drive is maximized. The optical disk drive device according to claim 1, wherein 3. The optical disk drive device according to claim 1, wherein a control system of the optical disk is a sampled servo system. 4. The optical disk drive according to claim 2, wherein the pre-pit is a clock pit.