JPH0793907A - Optical disk apparatus - Google Patents

Abstract

PURPOSE:To achieve a better withdrawal of the frequency of a PLL circuit without worsening an error rate in the generation of a reproduction data by a method wherein a gain of the PLL circuit is raised in a seek operation and the gain is returned to the original value upon the end of the seek operation. CONSTITUTION:When an optical disc is mounted on an optical disk apparatus to perform a seek operation, first, a switch of a charge pump 43 of a reproduction circuit 19 is turned ON with a CPU23 to increase a gain of a phase comparator 42 and a seek operation is started. After the end of the operation, the switch of the charge pump 43 is turned OFF with the CPU23 to decrease the gain of the comparator 42. Thus, during the seek operation, the gain of the comparator 42 is increased to check the repetition of the seek operation thereby shortening seek time totally. In addtion, after the seek operation, the gain of the comparator 42 is decreased thereby reducing an error rate of a reproduction signal processing circuit 41.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device.

[0002]

2. Description of the Related Art An optical disk device for optically writing information on a medium (disk) as a means for recording and storing information has a large storage capacity and is suitable for compactly storing a large amount of information.

In an optical disc used in such an optical disc device, various types of formats for recording data are adopted according to the purpose of use. Of these, M
-For an optical disk having a CAV (Modified-Constant Angle Velocity) format, when the optical disk device causes the optical head to seek to move to the target band, the reproduction data is reproduced. In order to determine the timing to read the data, it is necessary to obtain a reproduction clock that is in synchronization with the target band.

Conventionally, in order to obtain the above-mentioned reproduced clock, a face lock loop (hereinafter referred to as a PLL circuit) has been used. The PLL circuit detects the phase difference between the reproduction clock and the reproduction data and inputs the correction value to the VCO to generate the reproduction clock. Therefore,
When the optical head of the optical disk device reaches the target band (track-on), it can be quickly synchronized with the reproduction data.

However, when the optical head tracks on to a band other than the target band, it takes a long time to pull in the frequency of the PLL circuit, which may make it impossible to read the header. In such a case, the conventional optical disk device is
The seek operation was repeated several times until the header was read.

[0006]

As described above, in the conventional optical disk device as described above, when the optical head tracks on a band other than the target band and the header cannot be read, the system waits until the header is read. Since the seek operation is repeated, the seek time of the whole becomes long and there is a problem that it becomes redundant.

On the other hand, the above problem can be dealt with by increasing the gain of the PLL circuit and shortening the frequency pull-in time. However, if this is done, the error rate at the time of generating the reproduction data is increased. There was a problem that it would be expensive.

The present invention has been made to solve the above problems, and prevents the seek time from becoming redundant,
On the other hand, it is an object of the present invention to provide an optical disk device which does not increase the error rate when reproducing data is generated.

[0009]

In the optical disc device of the present invention, an optical recording medium obtained by scanning an optical recording medium on which information is optically recorded is scanned by an optical head, and the output signal of the optical head is used for the optical recording medium. A reproduction signal processing circuit for reproducing the recorded information, and a PLL circuit for the reproduction signal processing circuit to generate a clock signal serving as a reference for reproducing the information recorded on the optical recording medium from the output signal of the optical head. And switching means for changing the gain of the clock signal generating means.

[0010]

According to the present invention, the gain of the PLL circuit is increased during the seek operation, and after the seek operation is completed, the gain of the PLL circuit is returned to the original value.
It is possible to favorably pull in the frequency of the PLL circuit without deteriorating the rate.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an optical disk device according to an embodiment of the present invention.

In the figure, spiral or concentric recording tracks are formed on both surfaces of the optical disk 1 at substantially equal intervals. The optical disc 1 is rotated by the motor 2 at a constant speed, for example. This motor 2
Is controlled by the motor control circuit 18.

Recording and reproduction of information on the optical disc 1
As shown in FIG. 1, this is performed by an optical head 3 used as a recording / reproducing head. The optical head 3 is fixed to a drive coil 13 which constitutes a movable portion of the linear motor. The drive coil 13 is connected to the linear motor control circuit 17.

A linear motor position detector 26 is connected to the linear motor control circuit 17. This linear model
The position detector 26 outputs the current position signal by detecting the optical scale 25 provided on the optical head 3. Further, a permanent magnet (not shown) is provided in the fixed portion of the linear motor, and the drive coil 13 is excited by the linear motor control circuit 17 so that the optical head 3 moves in the radial direction of the optical disc 1. It is moved at a substantially constant speed.

An objective lens 6 is supported on the optical head 3 by a wire or a leaf spring. The objective lens 6 is moved in the focusing direction (optical axis direction of the lens) by the driving coil 5, and the driving coil (lens actuator coil) 4 moves the tracking direction across the recording track (the optical axis direction of the lens). Moved in the orthogonal direction).

The laser light generated by the semiconductor laser 9 driven by the laser control circuit 14 is passed through the collimator lens 11a, the half prism 11b, and the objective lens 6 onto the optical disk 1. Is irradiated. Then, the reflected light from the optical disc 1 is guided to the photodetector 8 via the objective lens 6, the half prism 11b, the condenser lens 10a, and the cylindrical lens 10b. The photodetector 8 is composed of photodetector cells 8a, 8b, 8c, 8d divided into four.

The output signal of the photodetector cell 8a of the photodetector 8 is supplied to one end of the adders 30a and 30c via the amplifier 12a, and the output signal of the photodetector cell 8b is supplied to the adders 30b and 30d via the amplifier 12b. The output signal of the photodetector cell 8c is supplied to one end of the
It is supplied to the other ends of b and 30c, and the output signal of the photodetection cell 8d is supplied to the other ends of the adders 30a and 30d via the amplifier 12d.

The output signal S1 of the adder 30a and the output signal S2 of the adder 30b are added by the adder 30e, and the sum signal b is supplied to the tracking control circuit 16.

The drive signal output from the tracking control circuit 16 is supplied to the drive coil 4 in the tracking direction. Then, in the optical head 3 that has accessed the track designated by the linear motor, the beam of light is moved by moving the objective lens 6 so as to correctly face this track.

The output signal of the adder 30c is supplied to the inverting input terminal of the differential amplifier OP2. The output signal of the adder 30d is supplied to the non-inverting input terminal of the differential amplifier OP2. As a result, the differential amplifier OP2 supplies the focusing control circuit 15 with a signal related to the focus point according to the difference between the adders 30c and 30d. The output signal of the focusing control circuit 15 is supplied to the focusing drive coil 5 so that the laser light is emitted from the optical disc 1.
It is controlled so that it is always just in focus.

Further, the sum signal of the outputs of the photodetector cells 8a to 8d of the photodetector 8 in the state where focusing and tracking are performed, that is, the output signals from the adders 30a and 30b are formed in a track shape. The irregularities of the formed pits (recorded information) are reflected. This signal is supplied to the reproducing circuit 19, and the reproducing circuit 19 reproduces image information and address information (track number, sector number, etc.).

As shown in FIG. 2, the reproduction circuit 19 receives the output signal of the optical head 3, binarizes the reproduction signal, and outputs reproduction data RDT, and reproduction data processing circuit 41. A phase comparator 42 for inputting RDT and comparing it with a reproduction clock (VCLKO) to generate signals CHG and DIS indicating a phase difference between both signals, and an output signal C of the phase comparator 42.
A charge pump 43 for changing the gain of the phase comparator 42 by inputting HG and DIS, an active filter 44a for filtering the output signal of the charge pump 43, and a low-pass filter.
A VCO (Vo) that receives the output signals of the pass filter 44b and the low pass filter 44b and outputs a clock signal (reproduced clock: VCLKO) of a frequency corresponding to the output.
ltage controlled oscillator) 45.

The reproduction signal processing circuit 41 inputs a reproduction clock which is an output signal of the VCO 45, takes timing with this reproduction clock as a reference, and generates reproduction data from the output signal of the optical head 3. The reproduction data is sent to the CPU 23 as well as being sent to the phase comparator 42 as described above, and subjected to predetermined data processing.

The charge pump 43 is composed of a signal line which is a combination of a diode and a resistor.
A switch SW1 is provided in the signal line including the switch 1. The switch SW1 is connected to the CPU23, and the CPU2
According to the control of 3, the optical head 3 is turned on when the seek operation is performed, and is turned off after the seek operation is completed. In the figure, the resistance values of the resistors a1 and b1 are a1 <b
It is 1. In addition, the charge pump 23 is a phase comparator 4
When the output signal CHG of No. 2 is low level, the current is drawn in, while when the output signal DIS of the phase comparator 42 is high level, the current is discharged.

The laser control circuit 14, the focusing control circuit 15, the tracking control circuit 16, and the linear motor.
The motor control circuit 17, the motor control circuit 18, the reproduction circuit 19 and the like are controlled by the CPU 23 via the bus line 20, and the CPU 23 performs a predetermined operation according to a program stored in the memory 24.

The D / A converter 22 is also used for exchanging information between the focusing control circuit 15, the tracking control circuit 16, the linear motor control circuit 17 and the CPU 23.

Next, the operation of the optical disk device configured as described above will be described with reference to the flowchart of FIG.

The optical disk 1 is mounted on the optical disk device,
When performing a seek operation, the CPU 23 first causes the reproduction circuit 19 to operate.
Turn on the switch SW1 of the charge pump 43 of
Increase the gain of the phase comparator 42 (step 30).
1). Then, the seek operation is started (step 30).
2).

When the seek operation is completed, the CPU 23
Turns off the switch SW1 of the charge pump 43,
The gain of the phase comparator 42 is decreased (step 30).
3, 304).

As described above, it is possible to increase the gain of the phase comparator 42 during the seek operation to suppress the repetition of the seek operation and shorten the overall seek time. On the other hand, since the gain of the phase comparator 42 is decreased after the seek operation, the error rate of the reproduction signal processing circuit 41 does not increase.

[0032]

As described above, according to the present invention, the P rate is not deteriorated without deteriorating the error rate at the time of reproducing data generation.
It is possible to favorably pull in the frequency of the LL circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a reproduction circuit of the optical disc device according to an embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the optical disc device according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Optical disc, 3 ... Optical head, 19 ... Playback circuit, 4
1 ... Reproduction signal processing circuit, 42 ... Phase comparator, 43 ... Charge pump, 44a ... Active filter, 44b ... Low pass filter, 45 ... VCO.

Claims (4)

[Claims] 1. A reproduction signal processing means for reproducing information recorded on the optical recording medium from an output signal of the optical head obtained by scanning an optical recording medium on which information is optically recorded with an optical head. A clock signal generating means for generating a clock signal which is a reference for reproducing the information recorded on the optical recording medium by the reproduction signal processing means based on the output signal of the optical head; and a gain of the clock signal generating means. An optical disc device comprising: a switching unit that changes 2. A reproduction signal processing means for reproducing the information recorded on the optical recording medium from the output signal of the optical head obtained by scanning the optical recording medium on which the information is optically recorded with the optical head. And a face-lock loop circuit for generating a clock signal as a reference for reproducing the information recorded on the optical recording medium by the reproduction signal processing means, based on the output signal of the optical head, and the face-lock loop circuit. Is provided on the output side of the phase comparator, absorbs current when the output of the phase comparator is low level, discharges current when the output of the phase comparator is high level, and performs the phase comparison. A light pump comprising: a charge pump having a changeover switch for changing the gain of the device; and means for changing over the changeover switch of the charge pump. Disk device. 3. A reproduction signal processing means for reproducing the information recorded on the optical recording medium from the output signal of the optical head obtained by scanning the optical recording medium optically recording the information with the optical head. And a face-lock loop circuit for generating a clock signal as a reference for reproducing the information recorded on the optical recording medium by the reproduction signal processing means, based on the output signal of the optical head, and the face-lock loop circuit. Is provided on the output side of the phase comparator, absorbs current when the output of the phase comparator is low level, discharges current when the output of the phase comparator is high level, and performs the phase comparison. And a charge pump having a changeover switch for changing the gain of the container, and turning on the changeover switch when the optical head performs a seek operation to end the seek operation. An optical disc device comprising a switching means for turning off the changeover switch after the completion. 4. A reproduction signal processing means for reproducing information recorded on the optical recording medium from an output signal of the optical head obtained by scanning an optical recording medium on which information is optically recorded with an optical head. And a face-lock loop circuit for generating a clock signal as a reference for reproducing the information recorded on the optical recording medium by the reproduction signal processing means, based on the output signal of the optical head, and the face-lock loop circuit. Is provided on the output side of the phase comparator, absorbs current when the output of the phase comparator is low level, discharges current when the output of the phase comparator is high level, and performs the phase comparison. And a charge pump having a changeover switch for changing the gain of the container, and turning on the changeover switch when the optical head performs a seek operation to end the seek operation. An optical disk apparatus comprising: a switching means for turning off the changeover switch after completion, and an active filter and a low-pass filter provided on the output side of the charge pump for filtering the output signal.