JP2001167508A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly and stably perform initial operation by accurately discriminating a track pitch. SOLUTION: Positional deviation between a beam spot 3 and a track on an optical disk is outputted as a tracking error signal 5 by a tracking error signal generation circuit 4. The tracking error signal 5 is inputted to a speed control circuit 6, and a drive signal is inputted to an optical pickup 2, then the speed control is performed. The tracking error signal 5 is inputted to an amplitude measurement circuit 7, and its output is inputted to a comparison circuit 8. A threshold value corrected with a correction circuit 10 based on the correction data stored in a storage circuit 9 is inputted to the comparison circuit 8, and the amplitude of the tracking error signal 5 is compared with the threshold value by the comparison circuit 8, and its output is inputted to a controller 11, and the track pitch of the optical disk 1 is discriminated with the controller 11.

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, and more particularly, to an optical disk device having a feature of determining a track pitch of an optical disk.

[0002]

2. Description of the Related Art In recent years, optical disk apparatuses capable of recording and reproducing information on a plurality of different types of optical disks have been developed. In such an optical disk device, the type of the optical disk is determined by detecting the track pitch of the optical disk.

As a method of discriminating optical discs having different track pitches, for example, in Japanese Patent Application Laid-Open No. 9-198777, an optical pickup is moved by a certain distance, and the number of tracks passed during that time is counted to determine the track pitch. ing.

In the case of Japanese Patent Application Laid-Open No. 9-198777,
A member such as a switch is required to detect the movement of a certain distance, which leads to an increase in cost.

[0005] For example, in Japanese Patent Application Laid-Open No. Hei 8-147611, a track pitch is determined based on the pit pattern shape of a sector mark based on optical information read by a sector mark detection circuit.

In Japanese Patent Application Laid-Open No. 8-147611, the track pitch is determined based on the pit pattern shape of the sector mark based on the optical information read by the sector mark detection circuit. Absent. Further, in this method, since the track pitch is not known before the tracking servo is pulled in, all the track pitches (1.6 μm, 1.3) are set with the loop gain for the provisionally determined track pitch.
(9 μm, 1.1 μm, 0.9 μm), the tracking servo system needs to be stable. However, 1.6μ
There is a gain difference of about 5 dB between m and 0.9 μm, and it is very difficult to form a stable tracking servo system with a loop gain for a tentatively determined track pitch.

On the other hand, a high density disk (track pitch 0.9 μm) and a low density disk (track pitch 1.6
There is also a method in which the discrimination of [μm, 1.39 μm, 1.1 μm) is performed by the amplitude of the tracking error signal at the time of off-track (at the time of seek). Since the modulation degree of the tracking error signal is lower in the high-density disk than in the low-density disk, the amplitude of the tracking error signal is smaller. Utilizing this, if the amplitude of the tracking error signal is below a certain threshold, it is determined that the disk is a high-density disk, and if it is above the threshold, it is determined that it is a low-density disk.

In the method of determining the track pitch based on the tracking error signal at the time of off-tracking (at the time of seeking), it is possible to determine the track pitch before pulling in the tracking servo.

[0009]

However, in the method of determining the track pitch based on the tracking error signal at the time of off-track (at the time of seeking), the threshold value used for the determination is fixed in all devices, so that the variation in the optical system causes There is a possibility that the amplitude of the tracking error signal varies and erroneous detection is performed. This will be described with reference to FIGS.

FIGS. 6 and 7 show waveforms of a tracking error signal in the first optical disk device, and FIGS. 8 and 9 show waveforms of a tracking error signal in the second optical disk device.

As shown in FIGS. 6 and 7, for example, in the first optical disk device, the threshold value Vth is Vth> V1 with respect to the amplitude value V1 of the tracking error signal on a 0.9 μm optical disk. The threshold value Vth satisfies Vth <V2 with respect to the amplitude value V2 of the tracking error signal on the 1.1 μm optical disk, and the type of the optical disk can be correctly determined.

On the other hand, as shown in FIGS. 8 and 9, for example, in the second optical disk apparatus, the amplitude value V1 of the tracking error signal on the optical disk of 0.9 μm has a threshold value due to variations in the optical system. Vth is Vth <V1, and the threshold value Vth is Vth <V2 with respect to the amplitude value V2 of the tracking error signal on the optical disk of 1.1 μm, and there is a problem that the type of the optical disk cannot be correctly determined.

Further, when an erroneous detection is made, the loop gain of the tracking servo is largely shifted. For this reason, the tracking servo cannot be stably pulled in, and a runaway or the like may occur. As a result, a retry operation occurs and the initial operation takes time. This is a significant performance penalty.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an optical disk apparatus capable of accurately determining a track pitch and performing a high-speed and stable initial operation.

[0015]

According to the present invention, there is provided an optical disk apparatus comprising: an optical pickup for irradiating a laser beam onto an optical disk to form a light spot; and a tracking error signal indicating a positional shift between a track of the optical disk and the light spot. A tracking error signal generating means for generating, an amplitude measuring means for measuring the amplitude of the tracking error signal, and a comparing means for comparing the amplitude of the tracking error signal with a predetermined threshold value; In an optical disk device for determining a track pitch of the optical disk based on an output, a storage unit storing correction data for correcting the threshold value; and the threshold value based on the correction data stored in the storage unit. Correction means for correcting the threshold value, and using the corrected threshold value to Constructed on the basis of the output to determine the track pitch.

[0016]

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

FIGS. 1 to 5 relate to an embodiment of the present invention. FIG. 1 is a block diagram showing a configuration of an optical disk device, and FIG. 2 shows a flow of processing for storing correction coefficients in a storage circuit of FIG. Flowchart, FIG. 3 is a waveform diagram showing a theoretical tracking error signal waveform in the process of FIG. 2, FIG. 4 is a waveform diagram showing a tracking error signal waveform on the reference disk in the process of FIG. 2, and FIG. 5 is a flowchart showing a flow of a normal operation sequence when a correction coefficient is stored in a storage circuit of FIG.

In the optical disk device of the present embodiment, as shown in FIG. 1, a light spot 3 is formed on an optical disk 1 by a laser beam irradiated from an optical pickup 2.

The positional deviation between the light spot 3 and the track on the optical disk 1 is output as a tracking error signal 5 by a tracking error signal generating circuit 4. The tracking error signal 5 is input to a speed control circuit 6, and a drive signal is input to the optical pickup 2 to perform speed control. Further, the tracking error signal 5 is inputted to the amplitude measuring circuit 7, and the output thereof is inputted to the comparing circuit 8.

On the other hand, the threshold value corrected by the correction circuit 10 based on the correction data stored in the storage circuit 9 is input to the comparison circuit 8, and the comparison circuit 8 compares the amplitude of the tracking error signal 5 with the threshold value. The output is input to the controller 11, and the controller 11 determines the track pitch (the type of the optical disk) of the optical disk 1.

The controller 11 controls the speed control circuit 6 and performs known tracking control and focus control on the optical pickup 2 so that information can be recorded on and reproduced from the optical disc 1.

Here, the amplitude measuring circuit 7 is constituted by an analog circuit such as a peak / bottom hold circuit. When a digital signal processor or the like is used, the amplitude may be obtained from the peak value and the bottom value by sampling the tracking error signal.

The comparison circuit 8 can be realized using a window comparator or the like. Further, the storage circuit 9 can be realized using an EEPROM, or may be realized using a trimmer resistor.

Next, the storage of the correction data in the storage circuit 9 will be described. As shown in FIG. 2, first, in an adjustment process using a reference disk at the time of production of an optical disk device, the controller 11 controls the speed control circuit 6 in step S1 according to an adjustment program, and
Is sought at a predetermined speed, and the amplitude V of the tracking error signal 5 of the reference disk at that time is measured.

Next, in step S2, the amplitude VREF of the predetermined tracking error signal 5 shown in FIG.
A ratio between the (theoretical value) and the measured amplitude V of the tracking error signal 5 is obtained to calculate a correction coefficient k. Therefore, the correction coefficient k is k = V / VREF.

Then, in step S3, the threshold value is corrected using the correction coefficient k. Assuming that the threshold value at the time of design is Vth, the corrected threshold value Vth ′ shown in FIG. 4 is obtained as Vth ′ = k × Vth = (V / VREF) × Vth.

Next, in step S4, it is confirmed that the track pull-in has been performed normally after the correction, and when the process has been completed normally, the correction coefficient k is written in the storage circuit 9 in step S5.

As a result, in all of the shipped optical disk devices, the correction coefficient k for correcting the variation of the optical system is set.
Is stored in the storage circuit 9.

Next, a normal operation sequence will be described. The optical disk device starts up, and as shown in FIG.
In step S11, the correction coefficient k written in the storage circuit 9 at the time of the initialization is read, and in step S12, the corrected threshold value Vth 'is calculated.

Next, when the optical disk 1 is inserted into the apparatus, the controller 11 controls the speed control circuit 6 in step S13 to cause the optical pickup 2 to seek at a predetermined speed, and to perform a seek operation at a predetermined speed. The amplitude V of the tracking error signal 5 of the middle reference disk is measured. The tracking error signal 5 is measured during a seek operation at a predetermined speed, and the track pitch is determined based on the corrected threshold value Vth 'to perform track pull-in.

Generally, since the amplitude of the tracking error signal 5 from the tracking error signal generation circuit 4 has a high-frequency cutoff characteristic, the amplitude of the tracking error signal 5 is attenuated when a seek operation is performed at a high speed, and the measurement is performed correctly. become unable. In consideration of this, it is desirable that the seek speed at the time of measuring the tracking error signal 5 be a constant speed that is not affected by the frequency characteristics of the tracking error signal generation circuit 4. In this way, the amplitude of the tracking error signal 5 can be measured without being affected by the frequency characteristics of the tracking error signal generation circuit 4.

As described above, in the present embodiment, the correction coefficient k for correcting the variation of the optical system of the optical disk device is stored in the storage circuit 9. Therefore, before the tracking servo is pulled in, the influence of the variation of the optical system is reduced. The track pitch can be accurately determined without receiving the signal, and a high-speed and stable initial operation can be performed.

[0033]

As described above, according to the present invention, there is an effect that the track pitch can be accurately determined, and a high-speed and stable initial operation can be performed.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a flow of processing for storing a correction coefficient in a storage circuit of FIG. 1;

FIG. 3 is a waveform chart showing a waveform of a theoretical tracking error signal in the processing of FIG. 2;

FIG. 4 is a waveform chart showing a waveform of a tracking error signal on a reference disk in the processing of FIG. 2;

FIG. 5 is a flowchart showing a flow of a normal operation sequence when a correction coefficient is stored in the storage circuit of FIG. 1;

FIG. 6 is a first explanatory diagram illustrating a method of determining a track pitch based on the amplitude of a tracking error signal in a conventional device.

FIG. 7 is a second explanatory diagram illustrating a method of determining a track pitch based on the amplitude of a tracking error signal in a conventional device.

FIG. 8 is a third explanatory diagram illustrating a method of determining a track pitch based on the amplitude of a tracking error signal in a conventional device.

FIG. 9 is a fourth explanatory diagram illustrating a method of determining a track pitch based on the amplitude of a tracking error signal in a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Optical pick-up 3 ... Optical spot 4 ... Tracking error signal generation circuit 5 ... Tracking error signal 6 ... Speed control circuit 7 ... Amplitude measurement circuit 8 ... Comparison circuit 9 ... Storage circuit 10 ... Correction circuit 11 ... Controller

Claims (2)

[Claims] An optical pickup for irradiating a laser beam on an optical disk to form a light spot; a tracking error signal generating means for generating a tracking error signal indicating a positional deviation between a track of the optical disk and the light spot; An amplitude measuring unit for measuring an amplitude of the error signal; and a comparing unit for comparing the amplitude of the tracking error signal with a predetermined threshold value, and determining a track pitch of the optical disk based on an output of the comparing unit. An optical disk apparatus for performing the correction, comprising: a storage unit storing correction data for correcting the threshold value; and a correction unit for correcting the threshold value based on the correction data stored in the storage unit. Determining the track pitch based on the output of the comparing means using the threshold value An optical disc device characterized by performing: 2. The apparatus according to claim 1, further comprising speed control means for moving the pickup at a predetermined speed with respect to the track of the optical disk, wherein the measurement of the amplitude of the tracking error signal is performed during the movement at a predetermined speed. The optical disk device according to claim 1.