KR20050001846A - Method for discriminating a kind of disc - Google Patents

Abstract

PURPOSE: A method for discriminating the kind of a disc is provided to discriminate the kind of a loaded disc based on a tracking error signal detected while a focusing servo is switched on and an object lens is being shifted vertically to a track of a disc. CONSTITUTION: The method comprises several steps. It is checked whether a focusing servo is switched on(S20). A tracking error signal is detected while a data reader is moved along a direction of a disc track or vertically to a disc track(S22). The sort of the disc is determined on a basis of the detected tracking error signal(S30). The tracking error signal is generated when the data reader crosses the disc track. The number of the tracks caused by the detected tracking signal is compared with a set value.

Description

{Method for discriminating a kind of disc}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to disc type discrimination. In particular, in an optical disc driver capable of playing both a digital versatile disc (DVD) and a compact disc (CD), track pitches of a DVD and a CD are included. Focusing on the fact that are different from each other, a method of determining the type of mounted disc using the tracking error signal detected while shifting the objective lens in a direction perpendicular to the track on the disc while the focusing servo is On It is about.

The existing disc type discrimination method mainly uses the fact that the position of the recording layer where data is recorded is different from the CD and the DVD. Specifically, the thickness of the transparent film is 1.2 mm for the CD and 0.6 mm for the DVD, and the focal lengths are different from the objective lens of the optical pickup. In other words, the optical system of the optical pickup and the recording layer of the disk are in focus so that the relative positions of the objective lens and the disk which can read data from the disk are different. Therefore, if the objective lens of the optical pickup is reciprocated in the direction perpendicular to the surface of the disk, the relative positions of the recording layer of the disk and the objective lens of the optical pickup corresponding to the point where the signal reflected from the recording layer of the disk occurs are Take advantage of the differences.

As shown in FIG. 1, when the driving current (F +) is applied to the focusing actuator and the focusing error signal is observed while the objective lens is reciprocated in the direction perpendicular to the disk plane, the objective lens is focused and the S-curve is generated. The positions of the discs and the recording layers are different in the case of DVD and CD. In the time axis, when the objective lens reciprocates in the direction perpendicular to the disk plane, the CD and DVD are different from each other when the S-curve or RF signal is generated or when the focusing servo is turned on. Therefore, the prior art (KRP 96-48021, KRP 96-50022, KRP 98-41088) is used to determine the type of disc using the difference in the time that the signals are generated during the reciprocating motion of the objective lens.

However, this conventional technology causes the following problems.

First, since the focusing actuator is raised or lowered at least two times to determine the disc type, it takes a long time to make a determination.

Second, there is a weak point in the external shock generated during the reciprocating actuator.

Therefore, the present invention was created to solve the above problems, and focuses on the fact that the track pitches of the DVD and the CD are different from each other, so that the objective lens is perpendicular to the track on the disc while the focusing servo is On. The present invention relates to a method for determining the type of a mounted disc using a tracking error signal detected while shifting.

FIG. 1 is a waveform diagram illustrating a focusing error and a tracking error signal for a method of determining a disc type using a conventional focusing error signal.

2 is a waveform diagram illustrating a focusing error and a cracking error signal by the disc type determining method according to the present invention;

Figure 3 shows the flow of a preferred embodiment of the disc type determination method according to the present invention.

According to an aspect of the present invention, there is provided a method of determining a disc type, the method comprising: checking an on state of a focusing servo; Detecting a tracking error signal while shifting the reading means in a direction perpendicular to the track direction; And determining the type of the disc based on the detected tracking error signal.

Hereinafter, a disc type determination method according to the present invention will be described with reference to the accompanying drawings.

When the focusing servo is turned on and current (T +) is sent to the tracking actuator to shift the objective lens in a direction perpendicular to the track on the disc, information about the pitch of the track on the disc traversed by the objective lens is a tracking error. Appears in the signal. When the objective lens traverses the track at a constant speed as shown in FIG. 2, the pitch of the tracking-error zero crossing (TZC) signal obtained by slicing the tracking error signal to zero level, that is, time It can be seen that the interval represents the track pitch. Since the track pitches of DVD and CD differ from 0.74um and 1.6um, respectively, by measuring the time interval of the TZC signal while moving the objective lens at a constant speed, the track pitch of the mounted disc can be known and the type of the mounted disc is also determined. can do.

In addition, when the objective lens is moved by a certain distance across the track on the disc, the number of tracks traversed from the TZC signal can be counted so that the track pitch on the mounted disc can be calculated using the same. Can be determined. For example, moving an objective lens about 100um in a direction perpendicular to tracks on a disc would theoretically traverse 135 tracks for a DVD and 62.5 tracks for a CD, so from the number of tracks obtained from the TZC signal, The track pitch on the mounted disc can be calculated and the type of mounted disc can be determined.

That is, the present invention is characterized in that the type of disc is determined by using a tracking error signal containing information on tracks on the disc traversed by the objective lens.

On the other hand, when the focusing servo is on, the objective lens is placed in a direction parallel to the

Even when the tracking error signal is detected in the non-moving state, a signal similar to the tracking error signal generated when the objective lens crosses the track is generated. This is called disc eccentricity. Disc eccentricity occurs because the physical center of the disc and the center of the track recorded on the disc do not coincide in the disc production process, or the spindle motor axis and the disc center do not coincide when the disc is fired. According to the standard, the allowable disc eccentricity is 125um for CD and 100um for DVD. Therefore, there is a case where it is necessary to consider the eccentricity of the mounted disc in the method of determining the disc type by using the track pitch detected while moving the objective lens in a direction perpendicular to the track on the disc while the focusing servo is on.

Therefore, when the focusing servo is turned on, the tracking error signal is detected while the objective lens is not moved in a direction parallel to the disk surface, and the number of times the objective lens crosses the track by the disc eccentricity while the mounted disk is rotated halfway. Obtain Then, the tracking error signal is detected while moving the objective lens in a direction perpendicular to the track on the disc, and the number of tracks traversed by the objective lens is obtained from this. The track pitch of the mounted disc is obtained by considering the number of tracks traversed by the objective lens and the number of disc eccentricities obtained, and the type of disc is determined from this.

On the other hand, even when it is determined whether the mounted disc is a DVD or a CD, it is necessary to further determine the detailed disc type. In the case of a DVD, it is necessary to determine whether it is a single layer DVD or a dual layer DVD, and in the case of a CD, it is necessary to determine whether it is a general CD or a CD-RW. This can be determined using the magnitude of the tracking error signal detected while the focusing servo is on and the magnitude of the reproduction RF signal. That is, in the case of a DVD, since the magnitude of the reproduced RF signal and the tracking error signal is different due to the difference in reflectance between the recording layers of the single layer DVD and the dual layer DVD, it is possible to distinguish between the single layer and the dual layer. In the case of the CD, since the reflectance is different in the recording layers of the normal CD and the CD-RW, it is possible to distinguish whether the CD is a normal CD or a CD-RW using the magnitude of the reproduction RF signal and the tracking error signal.

3 illustrates a flow of a preferred embodiment of the disc type determining method according to the present invention. Hereinafter, the disc type determining method of FIG. 3 according to the present invention will be described in detail with reference to FIG. 2.

When the disk is mounted, the spindle motor (Spindle motor) is rotated at a constant speed (S10). In the optical disc driver capable of playing both DVD and CD, the first disc is expected to be DVD, so the LD used for DVD playback is first turned on (S11). At this time, since the type of the loaded disk is not known yet, the output power of the LD is set to a high gain mode. Subsequently, a current is flowed through the focusing actuator so that the focus of the beam from the LD, which is formed below the surface of the disk, is concentrated on the recording layer of the disk, and the objective lens is gradually raised in the direction close to the disk (S12).

The focusing error signal is continuously detected while raising the objective lens. The smallest S-curve, which occurs first among the continuously detected focusing error signals, is a signal generated by reflection from the surface of the disk and is ignored. Then, when the focusing error signal becomes larger than a certain level and then decreases again, it is determined that the position of the objective lens is close to the position where the beam from the LD will focus on the recording layer of the disc. Since the beam focuses precisely on the recording layer of the disc at the moment when the smaller focusing error signal crosses the zero level, the focusing servo loop is closed to turn on the focusing servo. (S12). Then, it is checked whether the focusing servo loop is closed (S20).

If a DVD is mounted, the focusing servo will be on unless other special problems occur. However, when the CD is mounted, it is impossible to predict whether the focusing servo will be turned on or not.

Therefore, when the focusing servo is turned on, it is tentatively determined that the DVD disk is mounted and the next step is performed. However, when the focusing servo is turned off, it is determined that the CD is loaded and the LD for turning off the DVD is turned off, and instead, the LD for turning on the CD is turned on (S21). In the state where the LD for CD playback is turned on, the operation of turning on the focusing servo while raising the objective lens as described above is repeated (S12). At this time, when the focusing servo is turned on (S20), it is tentatively determined that the CD is mounted and performs the next step.

However, even in this case, when the focusing servo is turned off (S20), after turning off the LD for CD playback and turning on the LD for DVD playback, the above-described operations S12 and S20 are repeated, and in some cases, S21 and S12. And the operation S20 is repeated. If the focusing servo is turned off more than a certain number of times, it is determined that an error other than a DVD or CD is inserted.

On the other hand, when the focusing servo is turned on, the disc type may be determined tentatively, but the focusing servo may be turned on with respect to the CD while the LD for the DVD playback is turned on. Since the focusing servo may be turned on for the DVD while the LD is turned on, the following steps for disc type determination should be performed for more accurate judgment.

When the focusing servo is turned on, a current flows through the tracking actuator to detect a tracking error signal while moving the objective lens at a constant speed in a direction perpendicular to the track on the disk (S22). The pitch of the tracking error signal, that is, the time interval, is calculated from the TZC signal obtained from the detected tracking error signal to obtain a track pitch on the mounted disc (S22). From the obtained track pitch on the loaded disc, it is determined whether the loaded disc is a DVD or a CD (S30).

If it is determined whether the loaded disk is a DVD or a CD, it is discriminated whether it is a single layer DVD, a dual layer DVD, a general CD or a CD-RW. To this end, while the focusing servo is turned on, the magnitude of the tracking error signal and the RF reproduction signal is detected, and the magnitudes of the detected tracking error signal and the RF reproduction signal are compared with the magnitudes of the preset tracking error signal and the RF reproduction signal. It is determined whether the mounted disk is a single layer or a dual layer (S31), or whether it is a general CD or CD-RW (S32).

Preferred embodiments of the present invention described above have been disclosed for the purpose of illustration, and those skilled in the art can improve, change, substitute, or modify various technical embodiments within the spirit and scope of the present invention disclosed in the appended claims. Addition may be possible.

The disc type discriminating method according to the present invention as described above is a useful invention that can shorten the time for disc type discrimination and quickly reproduce the mounted disc, and also disc type can be determined even in the event of an external impact.

Claims (3)

Checking an on state of a focusing servo; Detecting a tracking error signal while moving the reading means in a direction perpendicular to the track direction; And And determining the type of the disc based on the detected tracking error signal. The method of claim 1, And the step (3) determines the type of disc at a time period of a tracking error signal generated when the reading means crosses the tracks. The method of claim 1, In the third step, the type of disc is determined by comparing the number of tracks by the tracking signal detected when the reading means is moved by a predetermined distance in a direction perpendicular to the track direction. Type determination method.