Optical disc system and method for controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information

Optical disc systems and methods for controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information are provided. For example, an optical disc system includes an optical pickup that includes a tracking actuator, a focus actuator, and an objective lens and radiates a laser beam onto the optical disc to detect light reflected from the optical disc. The optical disc system also includes a radio frequency amplifier, a sled motor, a servo driver, and a servo signal processor that includes an optical pickup movement determiner and outputs a servo control signal, the optical pickup movement determiner determining from a track-related signal whether tracks are detected on the optical disc at a current position of the optical pickup and outputting a track determination signal indicating whether the optical pickup has moved to the innermost perimeter of the optical disc, based on the determination result.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No. 2003-21420, filed on Apr. 4, 2003, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates, generally, to an optical disc system, and more particularly, to an optical disc system and method for controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information.

BACKGROUND

As shown inFIG. 1, an optical disc11, such as a compact disc (CD) or a digital versatile disc (DVD), is generally divided into three areas: a lead-out area, a data area, and a lead-in area. The lead-out area includes information indicating an end track. The data area includes audio information, video information, and so forth. The lead-in area includes a list of the information recorded in the data area, i.e., a table of contents (TOC) including information such as addresses of start and end tracks, and other various types of information related to the optical disc11.

A micro controller unit (MCU) of a conventional optical disc system controls movement of an optical pickup to an innermost perimeter of the optical disc11to read the TOC information when the optical disc11is loaded into the conventional optical disc system. The conventional optical disc system also uses a limit switch to control movement of the optical pickup to the innermost perimeter of the optical disc11.

FIG. 2is a block diagram of a conventional optical disc system including a limit switch. Referring toFIG. 2, an optical disc system10includes an optical pickup12, a radio frequency (RF) amplifier13, a digital signal processor (DSP)14, a servo signal processor (SSP)15, a MCU16, a digital-to-analog converter (DAC)17, a servo driver18, a spindle motor23, a sled motor24, and a limit switch25. The servo driver18includes a focus servo driver19, a tracking servo driver20, a sled servo driver21, and a spindle servo driver22. The limit switch25is positioned in the vicinity of the innermost perimeter of the optical disc11. One node of the limit switch25is grounded, and the other node of the limit switch25is connected to the MCU16.

FIG. 3is a timing diagram showing major signals used to move the optical pickup12of the optical disc system10ofFIG. 2to the innermost perimeter of the optical disc11. As shown inFIG. 3, the limit switch25outputs a limit signal LMS with a predetermined voltage level when the limit switch25is switched off. The limit switch25outputs the limit signal LMS with a ground voltage level when the limit switch25is switched on.

The limit switch25is switched on when the sled motor24moves the optical pickup12to the innermost perimeter of the optical disc11, and thus the optical pickup12is connected to the limit switch25. As a result, the limit switch25outputs the limit signal LMS with the ground voltage level to the MCU16. When the MCU16receives the limit signal LMS with the ground voltage level, the MCU16determines that the optical pickup12has moved to the innermost perimeter of the optical disc11and outputs a predetermined control signal to the SSP15so as to stop operation of the sled motor24. Here, the sled motor24is controlled by a voltage level of a control signal SLD output from the sled servo driver21. In more detail, as shown inFIG. 3, when the control signal SLD has a less voltage level than a predetermined reference voltage level, the sled motor24rotates in a reverse direction. When the control signal SLD has the same voltage level as the predetermined reference voltage level, the sled motor23stops its rotation operation.

Meanwhile, to make optical disc systems lighter and slimmer, various methods have been investigated to control the movement of an optical pickup to an innermost perimeter of an optical disc without using a limit switch. For example, one method is to control the movement of the optical pickup to the innermost perimeter of the optical disc using sub-Q data recorded on the optical disc. Sub-Q data refers to information recorded in a data area of the optical disc and includes, for example, information on time required for reproducing the recorded data. In this method, sub-Q data is read at predetermined intervals in the data area while the optical pickup moves toward the innermost perimeter of the optical disc, a current position of the optical pickup is calculated from the read sub-Q data, and the optical pickup is moved to the innermost perimeter of the optical disc. The problem with this method is that a focus servo, a tracking servo, a spindle servo, and a sled servo must be driven to actuate the moving parts of the optical disc system, and the sub-Q data must be iteratively read. Thus, it takes a long time to read TOC information.

Another example of a method of controlling movement of an optical pickup to the innermost perimeter of an optical disc without using a limit switch is disclosed in U.S. Pat. No. 5,173,887. In this method, the distance the optical pickup must move to get to the innermost perimeter of the optical disc is determined experimentally for various starting positions and put into a table. During operation of the optical pickup, the starting position is determined by reading sub-Q data from the optical disc. Then, the distance to the innermost perimeter of the optical disc is obtained from the table, and the optical pickup is moved the obtained distance toward the innermost perimeter of the optical disc. The problem with this method is that the distances stored in the table are imprecise and sometimes inaccurate. Also, additional memory is required to store the table.

Therefore, a need exists for an optical disc system and a method for reducing the time required for reading TOC information and accurately controlling the movement of an optical pickup to an inner perimeter of an optical disc.

SUMMARY OF THE INVENTION

Exemplary embodiments of the invention generally include an optical disc system and method for reducing time required for reading TOC information and accurately controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information, wherein a determination as to whether the optical pickup has moved to the innermost perimeter of the optical disc is made based on whether tracks are detected on the optical disc at the current position of the optical pickup.

According to an exemplary embodiment of the present invention, an optical disc system for controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information includes an optical pickup that radiates a laser beam onto the optical disc to detect light reflected from the optical disc and includes a tracking actuator, a focus actuator and an objective lens, a radio frequency amplifier that converts the reflected light into an electric signal to output a track-related signal, a sled motor that moves the optical pickup toward an inner or outer perimeter of the optical disc in response to a sled servo drive signal, a servo driver that outputs the sled servo drive signal and a tracking servo drive signal in response to one of a first servo control signal and a second servo control signal, and a servo signal processor that includes an optical pickup movement determiner and outputs one of the first servo control signal and the second servo control signal, the optical pickup movement determiner determining from the track-related signal whether tracks are detected on the optical disc at a current position of the optical pickup and outputting a track determination signal indicating whether the optical pickup has moved to the innermost perimeter of the optical disc, based on the determination result. The tracking actuator moves the objective lens toward the inner or outer perimeter of the optical disc in response to the tracking servo drive signal.

According to another exemplary embodiment of the present invention, an optical disc system for controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information includes an optical pickup that radiates a laser beam onto the optical disc to detect light reflected from the optical disc and includes a tracking actuator, a focus actuator and an objective lens, a radio frequency amplifier that converts the reflected light into an electric signal to output a track-related signal, a sled motor that moves the optical pickup toward an inner perimeter of the optical disc in response to a first sled servo drive signal, and toward an outer perimeter of the optical disc in response to a second sled servo drive signal, a servo driver that outputs the first sled servo drive signal and a first tracking servo drive signal in response to a first servo control signal, and outputs the second sled servo drive signal and a second tracking servo drive signal in response to a second servo control signal, a micro controller unit that outputs a limit check command, determines from the track-related signal whether tracks are detected on the optical disc at a current position of the optical pickup and, if it is determined that tracks are not detected, outputs a limit check completion signal, and a servo signal processor that outputs the first servo control signal in response to the limit check command, and outputs the second servo control signal in response to the limit check completion signal. The tracking actuator moves the objective lens toward the inner perimeter of the optical disc in response to the first tracking servo drive signal and toward the outer perimeter of the optical disc in response to the second tracking servo drive signal.

According to still another exemplary embodiment of the present invention, a method of controlling movement of an optical pickup of an optical disc system includes a micro controller unit outputting a limit check command, a servo signal processor driving a focus servo using a focus actuator of an optical pickup in response to the limit check command, applying a reverse kick voltage to a sled motor, applying a reverse jump voltage to a tracking actuator of the optical pickup, an optical pickup movement determiner of the servo signal processor receiving a track-related signal and determining whether tracks are detected on an optical disc at a current position of the optical pickup, if it is determined that tracks are detected, returning to the steps of receiving of the track-related signal and determining whether the tracks are detected on the optical disc, and if it is determined that tracks are not detected, stopping operations of the sled motor and the tracking actuator.

These and other exemplary embodiments, features, aspects, and advantages of the present invention will be described and become apparent from the following detailed description of the exemplary embodiments when read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. Like reference numerals denote like members throughout the drawings.

FIG. 4is a block diagram of an optical disc system for controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information, according to an exemplary embodiment of the present invention. Referring toFIG. 4, an optical disc system100includes an optical pickup102, an RF amplifier103, a DSP104, an SSP105, an MCU106, a DAC107, a servo driver108, a spindle motor113, and a sled motor114.

The optical pickup102radiates a laser beam onto tracks of an optical disc101and detects light reflected from the optical disc101. The RF amplifier103converts the reflected light into an electric signal to output a digital data signal EFM, a track zero-cross signal TZC, a mirror signal MIRR, and a track change signal TRCNT. Although not shown inFIG. 4, the RF amplifier103also outputs various error signals such as a tracking error signal TE, a focus error signal FE, and the like.

Here, the track zero-cross signal TZC is generated when the optical pickup102hones in on a track. The mirror signal MIRR is generated in a non-data portion between tracks when the optical pickup102reads data from the optical disc101. A track change signal generator200ofFIG. 5generates the track change signal TRCNT in response to the track zero-cross signal TZC and the mirror signal MIRR. The track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT will be explained later in more detail with reference toFIGS. 5 and 6.

The DSP104recovers an audio signal from the digital data signal EFM, and the DAC107converts the audio signal into an analog signal and outputs the analog signal. The DSP104also detects a frame synchronous pattern from the digital data signal EFM and outputs a spindle motor control signal VCTL based on the frame synchronous pattern to the SSP105.

The SSP105generates a focus servo control signal FCTL from the focus error signal FE and outputs the focus servo control signal FCTL to a focus servo driver109. The SSP105generates a tracking servo control signal TCTL from the tracking error signal TE and outputs the tracking servo control signal TCTL to a tracking servo driver110. The SSP105also generates a spindle servo control signal SPCTL in response to the spindle motor control signal VCTL and outputs the spindle servo control signal SPCTL to a spindle servo driver112. The SSP105is controlled by the MCU106so as to generate a sled servo control signal SCTL and output the sled servo control signal SCTL to a sled servo driver111. Here, although not shown inFIG. 4, the spindle servo control signal SPCTL includes first and second spindle servo control signals SPCTL1and SPCTL2, the tracking servo control signal TCTL includes first and second tracking servo control signals TCTL1and TCTL2, and the sled servo control signal SCTL includes first, second, and third sled servo control signals SCTL1, SCTL2, and SCTL3.

The MCU106outputs a limit check command MLT and predetermined control signals to the SSP105so as to move the optical pickup102to the innermost perimeter of the optical disc101. The predetermined control signals are a selection signal SEL, a first enable signal EN1, first data DATA1, and second data DATA2. Although not shown inFIG. 4, the MCU106outputs other control signals as well.

The servo driver108includes the focus servo driver109, the tracking servo driver110, the sled servo driver111, and the spindle servo driver112.

The focus servo driver109outputs a focus servo drive signal FODRV in response to the focus servo control signal FCTL. A focus actuator (not shown) inside the optical pickup102moves the optical pickup102up and down in response to the focus servo drive signal FODRV.

The tracking servo driver110outputs a tracking servo drive signal TRDRV in response to the tracking servo control signal TCTL. In response to the tracking servo drive signal TRDRV, a tracking actuator (not shown) inside the optical pickup102moves an objective lens31ofFIG. 14inside the optical pickup102in a radial direction so that the laser beam stays focused on a predetermined track.

The sled servo driver111outputs a sled servo drive signal SLDRV in response to the sled servo control signal SCTL. The sled motor114moves the optical pickup102from an inner perimeter of the optical disc101to an outer perimeter of the optical disc101or from the outer perimeter to the inner perimeter in response to the sled servo drive signal SLDRV.

The spindle servo driver112outputs first and second spindle servo drive signals SPDRV1and SPDRV2in response to the first and second spindle servo control signals SPCTL1and SPCTL2, respectively.

The spindle motor113rotates the optical disc101at a constant linear velocity (CLV) or a constant angular velocity (CAV) in response to the first spindle servo drive signal SPDRV1. In addition, the spindle motor113stops the rotation of the optical disc101in response to the second spindle servo drive signal SPDRV2.

The operation of the optical disc system100with the above-described structure will now be described with reference toFIGS. 4,7, and9A.

FIG. 7is a flowchart illustrating an operation1000of the optical disc system100ofFIG. 4moving the optical pickup102to the innermost perimeter of the optical disc101.

In step1100, the MCU106outputs the limit check command MLT. The SSP105then outputs the focus servo control signal FCTL, the first sled servo control signal SCTL1, and the first tracking servo control signal TCTL1in response to the limit check command MLT.

In step1200, the focus servo driver109outputs the focus servo drive signal FODRV in response to the focus servo control signal FCTL. Then, the focus actuator of the optical pickup102moves the optical pickup102up and down so as to adjust the focus of the laser beam on the optical disc101in response to the focus servo drive signal FODRV. In addition, the SSP105outputs the first spindle servo control signal SPCTL1to rotate the optical disc101at the CLV or CAV or outputs the second spindle servo control signal SPCTL2to stop rotation of the optical disc101.

In step1300, the sled servo driver111outputs to the sled motor114the sled servo drive signal SLDRV with a voltage level less than a second reference voltage level VREF2, i.e., a reverse kick voltage level, as shown inFIG. 9A, in response to the first sled servo control signal SCTL1. The sled motor114moves the optical pickup102toward the inner perimeter of the optical disc101in response to the sled servo drive signal SLDRV. Here, a rotation direction of the sled motor114is determined by the voltage level of the sled servo drive signal SLDRV. The sled motor114rotates in a forward direction when the voltage level of the sled servo drive signal SLDRV is greater than the second reference voltage level VREF2, in a reverse direction when the voltage level of the sled servo drive signal SLDRV is less than the second reference voltage level VREF2, and stops rotating when the voltage level of the sled servo drive signal SLDRV is equal to the second reference voltage level VREF2.

Prior to step1300, as shown inFIG. 9A, the sled servo driver111may output the sled servo drive signal SLDRV with a voltage level greater than the second reference voltage level VREF2, i.e., a forward kick voltage level, for a predetermined period of time, i.e., as shown in section B ofFIG. 9A, in response to the third sled servo control signal SCTL3. Here, the sled motor114moves the optical pickup102to the outer perimeter of the optical disc101in response to the sled servo drive signal SLDRV, as shown in section B ofFIG. 9A. This is to prevent the sled motor114from being overloaded when the optical pickup102is positioned at the innermost perimeter of the optical disc101in an initial state.

In step1400, as shown inFIG. 9A, the tracking servo driver110outputs to the tracking actuator the tracking servo drive signal TRDRV with a voltage level less than a first reference voltage level VREF1, i.e., a reverse jump voltage level, in response to the first tracking servo control signal TCTL1. Then, the tracking actuator of the optical pickup102moves the objective lens31of the optical pickup102toward the inner perimeter of the optical disc101in response to the tracking servo drive signal TRDRV.

Here, the tracking actuator moves the objective lens31toward the inner or outer perimeter of the optical disc101depending on the voltage level of the tracking servo drive signal TRDRV. More specifically, the tracking actuator moves the objective lens31toward the inner perimeter of the optical disc101when the voltage level of the tracking servo drive signal TRDRV is less than the first reference voltage VREF1, toward the outer perimeter of the optical disc101when the voltage level of the tracking servo drive signal TRDRV is greater than the first reference voltage VREF1, and stops its operation when the voltage level of the tracking servo drive signal TRDRV is equal to the first reference voltage VREF1.

FIG. 14shows a case where the optical pickup102has moved to the innermost perimeter of the optical disc101and cannot move any more. Referring toFIG. 14, as depicted with a dotted line, when an objective lens31′ is installed in the center of the optical pickup102, the objective lens31′ is positioned over a lead-in area of the optical disc101. As a result, when the optical pickup102reaches the innermost perimeter of the optical disc101, the optical pickup102cannot output an RF signal detected from a non-track area of the optical disc101unless the objective lens31′ moves toward the inner perimeter of the optical disc101. Therefore, as depicted with a solid line, the objective lens31′ must move in the optical pickup102toward the inner perimeter of the optical disc101to the position indicated by reference numeral31.

The optical pickup102, while moving toward the inner perimeter of the optical disc101, radiates the laser beam onto the optical disc101and detects light reflected from the optical disc101. The RF amplifier103converts the reflected light into an electric signal to output track-related signals. The track-related signals include the track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT. InFIG. 4, the RF amplifier103outputs only the track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT. However, in a case of a blank CD on which data is not recorded, the RF amplifier103may output a virtual track signal for recording, i.e., a wobble signal WOBB.

In step1500, the SSP105receives one of the track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT, or in the case of the blank CD, the wobble signal WOBB.

In step1600, the SSP105determines whether tracks are detected on the optical disc101at the position of the optical pickup102. The SSP105outputs the second sled servo control signal SCTL2and the second tracking servo control signal TCTL2when the non-track area is detected on the optical disc101, i.e., when the optical pickup102reaches the innermost perimeter of the optical disc101. Step1600performed by the SSP105will be explained later in more detail with reference toFIGS. 8 through 10.

In step1700, in response to the second sled servo control signal SCTL2, the sled servo driver111outputs the sled servo drive signal SLDRV with a voltage level equal to the second reference voltage level VREF2to stop the operation of the sled motor114. Also, in response to the second tracking servo control signal TCTL2, the tracking servo driver110outputs the tracking servo drive signal TRDRV with a voltage level equal to the first reference voltage level VREF1to stop the operation of the tracking actuator. Here, the SSP105enables and outputs a track determination signal TRDET to the MCU106to inform the MCU106that the optical pickup102has reached the innermost perimeter of the optical disc101.

Next, the MCU106receives the track determination signal TRDET from the SSP105and performs a control operation to read TOC information from the optical disc101.

FIG. 5is a block diagram of a track change signal generator200of the RF amplifier103ofFIG. 4. Referring toFIG. 5, the track change signal generator200includes an edge detector201and a D flip-flop202. As shown inFIG. 6, the edge detector201generates and outputs a pulse signal CK_TZC at rising and falling edges of the track zero-cross signal TZC. The D flip-flop202receives the mirror signal MIRR as a D input and receives the pulse signal CK_TZC as a clock input. The D flip-flop202also outputs the track change signal TRCNT, as shown inFIG. 6, in response to the mirror signal MIRR and the pulse signal CK_TZC. As can be seen inFIG. 6, the track zero-cross signal TZC is a digital signal obtained by slicing the tracking error signal TE.

Step1600will be explained below, but first,FIG. 8is a block diagram of an optical pickup movement determiner300of the SSP105ofFIG. 4. Referring toFIG. 8, the optical pickup movement determiner300includes a multiplexer (MUX)301, a first counter302, a control signal generator303, a second counter304, a timer305, and a track determiner306.

The MUX301selects one of the track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT in response to the selection signal SEL output from the MCU106ofFIG. 4and outputs the selected signal to the first counter302and the second counter304. In the case of a blank CD, the MUX301outputs the virtual track signal for recording, i.e., the wobble signal WOBB.

The first counter302counts a number of times a signal is output from the MUX301, as shown in section A ofFIG. 9A, in response to the first enable signal EN1output from the MCU106. In addition, the first counter302outputs the accumulated count value as a first count value CNT1. Here, an additional control circuit in the SSP105may generate the first enable signal EN1in response to the limit check command MLT output from the MCU106.

The control signal generator303receives the first count value CNT1from the first counter302and compares the first count value CNT1with the first data DATA1received from the MCU106. The first data DATA1includes predetermined bits and refers to information on a number of tracks set by the MCU106. When the first count value CNT1is equal to the first data DATA1, the control signal generator303outputs a counting control signal CNT_CTL.

Here, in a case where data is recorded only in a portion of an inner area of the optical disc101, which may be a CD-writable (R), a CD-rewritable (RW), a DVD-RW, or the like, there are no tracks in an outer area of the disc. When the optical pickup102is positioned over the outer area, the optical pickup movement determiner300may incorrectly determine that the optical pickup102has moved to the innermost perimeter of the optical disc101. Thus, after the track zero-cross signal TZC, the mirror signal MIRR, or the track change signal TRCNT is output a number of times set by the MUX301, the first counter302and the control signal generator303are used so that the optical pickup movement determiner300starts determining whether tracks are detected on the optical disc101at the position of the optical pickup102. The first counter302stops its counting operation in response to the counting control signal CNT_CLT. The counting control signal CNT_CLT is applied as a hold signal to the first counter302.

The second counter304counts up or counts down the number of times the signal is output from the MUX301in response to a clock signal CLK and the counting control signal CNT_CLT. For example, assume that the signal output from the MUX301is the track change signal TRCNT. As shown inFIG. 9B, the second counter304counts up or counts down the track change signal TRCNT every period of the clock signal CLK according to a voltage level of the track change signal TRCNT and accumulates count values. The second counter304counts up the track change signal TRCNT when the track change signal TRCNT is at a high voltage level, and counts down the track change signal TRCNT when the track change signal TRCNT is at a low voltage level.

The result of the counting up and counting down of the second counter304can be represented with data of a predetermined number of bits, for example, 16-bit data of “16′h0000”, although the number of bits may vary. When a most significant bit of 16-bit data “0000˜FFFF” is inverted, the 16-bit data is changed into “8000˜0000˜7FFF”. Thus, when the count value of the second counter304is 16-bit data, the accumulated count value may be expressed with “8000˜0000˜7FFF”.

Here, when counting down, the second counter304counts from “0000” to “8000” and holds the count when the accumulated count value is “8000”. When counting normally, the second counter304counts from “0000” to “7FFF” and holds the count when the accumulated count value is “7FFF”. Accordingly, when the most significant bit of the accumulated count value of the second counter304is “1”, the second counter304performs the counting down operation a greater number of times than the number of times the counting up operation was performed. In contrast, when the most significant bit of the accumulated count value is “0”, the second counter304performs the counting up operation a greater number of times than the number of times the counting down operation was performed. Here, the most significant bit serves as a sign bit. In more detail, if the most significant bit is “1”, it is a positive sign bit. And, if the most significant bit is “0”, it is a negative sign bit.

The second counter304outputs the accumulated count value as a second count value CNT2. Here, the second counter304resets the second count value CNT2to “0000” and restarts the counting operation in response to a reset signal RST output from the timer305. The timer305receives the clock signal CLK and outputs the reset signal RST and a second enable signal EN2at predetermined time intervals. As shown inFIG. 9A, the timer305enables the second enable signal EN2at predetermined time intervals. The predetermined time intervals correspond to limit check periods set by the MCU106. Here, the timer305first outputs the second enable signal EN2and then outputs the reset signal RST after one period of the clock signal CLK.

The track determiner306receives the second count value CNT2and compares it with the second data DATA2received from the MCU106. The second data DATA2is a reference value set by the MCU106to determine whether tracks are detected on the optical disc101at the position of the optical pickup102. The number of bits of the second data DATA2is predetermined. For example, assume that the second data DATA2is 16-bit data. Here, the second data DATA2may be set to a predetermined value with a most significant bit of “1”.

Here, when the optical pickup102reaches the innermost perimeter of the optical disc101at which the non-track area is detected, as shown inFIG. 9A, the track change signal (TRCNT) with the low voltage level is successively output. As a result, the second counter304successively performs the counting down operation.

Accordingly, when the second count value CNT2has “1” as its most significant bit, and is less than the second data DATA2, the track determiner306determines that the optical pickup102has arrived at the innermost perimeter of the optical disc101. For example, when the second data DATA2is “9000” and the second count value CNT2is “8FFF”, the second count value CNT2has “1” as its most significant bit and is less than the second data DATA2. Thus, the track determiner306determines that the optical pickup102has reached the innermost perimeter of the optical disc101.

Thereafter, as shown inFIG. 9A, the track determiner306enables and outputs the track determination signal TRDET. In response to the track determination signal TRDET, a controller (not shown) of the SSP105outputs the second tracking servo control signal TCTL2and the second sled servo control signal SCTL2to the tracking servo driver110and the sled servo driver111, respectively, to end the limit check operation.

The MCU106performs the control operation to read the TOC information in response to the track determination signal TRDET. In more detail, the SSP105outputs the third sled servo control signal SCTL3to the sled servo driver111in response to a control signal (not shown) output from the MCU106. The sled servo driver111then outputs to the sled motor114the sled servo drive signal SLDRV with a voltage level greater than the second reference voltage level VREF2, as shown in section C ofFIG. 9A, in response to the third sled servo control signal SCTL3, so as to rotate the sled motor114in the forward direction. As a result, the optical pickup102moves toward the outer perimeter of the optical disc101and is positioned over the lead-in area of the optical disc101.

The track determiner306compares the second count value CNT2with the second data DATA2whenever the second enable signal EN2is enabled.

The second counter304stops its counting operation in response to the track determination signal TRDET, which is applied as a hold signal to the second counter304. The second counter304does not respond to the reset signal RST if it is received after receiving the track determination signal TRDET.

As previously described with reference toFIG. 8, the second counter304counts up the number of times the signal is output from the MUX301when the track change signal TRCNT is high, and counts down the number of times the signal is output from the MUX301when the track change signal TRCNT is low. However, it may be the other way around. That is, the second counter304may count down the number of times the signal is output from the MUX301when the track change signal TRCNT is high, and count up the number of times the signal is output from the MUX301when the track change signal TRCNT is low. In this case, the second data DATA2may be set to a predetermined value with the most significant bit of “0”. Thus, when the second count value CNT2has the most significant bit of “0” and is greater than the second data DATA2, the track determiner306determines that the optical pickup102has moved to the innermost perimeter of the optical disc101.

Step1600performed by the optical pickup movement determiner300having the above-described structure will now be described with reference toFIG. 10.

FIG. 10is a flowchart illustrating an example of step1600ofFIG. 7. Referring toFIG. 10, in step1601, the first counter302counts the number of times the track-related signal is output from the MUX301, accumulates count values, and outputs the result as the first count value CNT1in response to the first enable signal EN1.

In step1602, the control signal generator303determines whether the first count value CNT1is equal to the first data DATA1.

If, in step1602, it is determined that the first count value CNT1is equal to the first data DATA2, in step1603, the control signal generator303outputs the counting control signal CNT_CTL for starting the operation of the second counter304. Also, the first counter302holds its counting operation in response to the counting control signal CNT_CTL.

In step1604, the second counter304counts the number of times the track-related signal is output, accumulates the count value, and outputs the second count value CNT2in response to the counting control signal CNT_CTL.

In step1605, the timer305outputs the second enable signal EN2to inform the track determiner306that now is a limit check time. The track determiner306then determines in response to the second enable signal EN2whether tracks are detected on the optical disc101at the position of the optical pickup102.

In step1606, the track determiner306determines whether the sign bit of the second count value CNT2is “1”. If, in step1606, it is determined that the sign bit of the second count value CNT2is not “1”, the track determiner306does not enable the track determination signal TRDET. Thus, in step1607, the second counter304is reset by the reset signal RST output from the timer305and the optical pickup movement determiner300returns to step1604.

If, in step1606, it is determined that the sign bit of the second count value CNT2is “1”, in step1608, the track determiner306determines whether the second count value CNT2is less than the second data DATA2. Here, if it is determined that the second count value CNT2is greater than or equal to the second data DATA2, the track determiner306returns to step1607, and if it is determined that the second count value CNT2is less than the second data DATA2, in step1609, the track determiner306enables the track determination signal TRDET.

When the track determination signal TRDET is enabled, the MCU106determines that there are no tracks detected on the optical disc101at the current position of the optical pickup102, i.e., the optical pickup102has arrived at the innermost perimeter of the optical disc101. At this time, the SSP105stops the operations of the sled motor114and the tracking actuator.

As previously described, in step1608, the track determiner306compares the second count value CNT2with the second data DATA2. Alternatively, the track determiner306may measure a time for which the sign bit of the second count value CNT2remains at “1”. More specifically, If, in step1606, it is determined that the sign bit of the second count value CNT2is “1”, in an alternative exemplary embodiment to that shown inFIG. 10, the track determiner306may determine whether the sign bit of the second count value CNT2remains at “1” for a predetermined period of time. Here, if the sign bit of the second count value CNT2changes from “1” into “0” within the predetermined period of time, the track determiner306does not enable the track determination signal TRDET. Thus, in step1607, the second counter304is reset by the reset signal RST output from the timer305and returns to step1604. On the other hand, if the sign bit of the second count value CNT2remains at “1” for the predetermined period of time, in step1609, the track determiner306enables the track determination signal TRDET.

When the track determination signal TRDET is enabled, the MCU106determines that there are no tracks detected on the optical disc101at the current position of the optical pickup102, i.e., the optical pickup102has arrived at the innermost perimeter of the optical disc101. At this time, the SSP105stops the operations of the sled motor114and the tracking actuator.

FIG. 11is a block diagram of an optical disc system for controlling the movement of an optical pickup to an innermost perimeter of an optical disc using track information, according to another exemplary embodiment of the present invention. Referring toFIG. 11, an optical disc system400includes an optical pickup402, an RF amplifier403, a DSP404, an SSP405, an MCU406, a DAC407, a servo driver408, a spindle motor413, and a sled motor414.

The optical disc system400is identical in structure and operation to the optical disc system100ofFIG. 4except for the following point. In the optical disc system100, the SSP105receives the track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT from the RF amplifier103. However, in optical disc system400, the MCU406receives the track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT from an RF amplifier403.

FIG. 12is a flowchart illustrating a method of controlling the movement of the optical pickup of the optical disc system ofFIG. 11to the innermost perimeter of an optical disc, according to another exemplary embodiment of the present invention. Referring toFIGS. 11 and 12, operation2000of the optical disc system400will now be explained.

In step2100, the MCU406outputs a limit check command MLT to the SSP405.

In step2200, the SSP405outputs a focus servo control signal FCTL, a spindle servo control signal SPCTL, a sled servo control signal SCTL, and a tracking servo control signal TCTL in response to the limit check command MLT. Here, although not shown inFIG. 11, the spindle servo control signal SPCTL includes first and second spindle servo control signals SPCTL1and SPCTL2, the tracking servo control signal TCTL includes first and second tracking servo control signals TCTL1and TCTL2, and the sled servo control signal SCTL includes first, second, and third sled servo control signals SCTL1, SCTL2, and SCTL3. Here, the SSP405may output the first spindle servo control signal SPCTL1to rotate the optical disc401at a CLV or CAV, or the second spindle servo control signal SPCTL2to stop rotation the optical disc401. Also in step2200, a focus servo driver409outputs a focus servo drive signal FODRV in response to the focus servo control signal FCTL, and a focus actuator in the optical pickup402moves the optical pickup402up and down to focus a laser beam on an optical disc401in response to the focus servo drive signal FODRV.

In step2300, in response to the first sled servo control signal SCTL1, a sled servo driver411outputs a sled servo drive signal SLDRV with a voltage level lower than the second reference voltage level VREF2, i.e., a reverse kick voltage level. The sled motor414moves the optical pickup402toward an inner perimeter of the optical disc401in response to the sled servo drive signal SLDRV. However, prior to step2300, in response to a second sled servo control signal SCTL2, the sled servo driver411may output the sled servo drive signal SLDRV with a voltage level greater than the second reference voltage level VREF2, i.e., a forward kick voltage level, for a predetermined period of time. In this case, the sled motor414moves the optical pickup402toward an outer perimeter of the optical disc401in response to the sled servo drive signal SLDRV.

In step2400, a tracking servo driver410outputs the tracking servo drive signal TRDRV with a voltage level less than the first reference voltage VREF1, i.e., a reverse jump voltage level, in response to the first tracking servo control signal TCTL1. A tracking actuator in the optical pickup402moves the objective lens31ofFIG. 14in the optical pickup402toward the inner perimeter of the optical disc401in response to the tracking servo drive signal TRDRV.

Thereafter, the optical pickup402radiates the laser beam onto the optical disc401and detects light reflected therefrom, while moving toward the inner perimeter of the optical disc401. The RF amplifier403converts the reflected light into an electric signal to output the track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT as track-related signals. However, in the case of a blank CD, the RF amplifier403may output a virtual track signal for recording, i.e., a wobble signal WOBB.

In step2500, the MCU406receives one of the track zero-cross signal TZC, the mirror signal MIRR, and the track change signal TRCNT, or in the case of the blank CD, the wobble signal WOBB.

In step2600, the MCU406determines whether tracks are detected on the optical disc401at the current position of the optical pickup402. Here, for the determination2600, the MCU406performs the same operation as the optical pickup movement determiner300ofFIG. 8, using an internal program. If, in step2600, it is determined that tracks are not detected on the optical disc401, i.e., the optical pickup has moved to an innermost perimeter of the optical disc401, the MCU406outputs a limit check completion signal SVCTL to the SSP405. The SSP405then outputs the second sled servo control signal SCTL2and the second tracking servo control signal TCTL2in response to the limit check completion signal SVCTL. Step2600will be described in more detail below with reference toFIG. 13.

In step2700, in response to the second sled servo control signal SCTL2, the sled servo driver411outputs the sled servo drive signal SLDRV with a voltage level equal to the second reference voltage level VREF2to stop operation of the sled motor414. Also in step2700, in response to the second tracking servo control signal TCTL2, the tracking servo driver410outputs the tracking servo drive signal TRDRV with a voltage level equal to the first reference voltage level VREF1.to stop operation of the tracking actuator. Thereafter, the MCU406performs a control operation to read TOC information from the optical disc401. For example, the MCU406outputs a predetermined control signal (not shown) to the SSP405. The SSP405then outputs the third sled servo control signal SCTL3to the sled servo driver411in response to the predetermined control signal. The sled servo driver411outputs to the sled motor414the sled servo drive signal SLDRV with a voltage level greater than the second reference voltage level VREF2for a predetermined period of time. The sled motor414rotates in a forward direction in response to the sled servo drive signal SLDRV. As a result, the optical pickup402moves to the outer perimeter of the optical disc401and is positioned over a lead-in area of the optical disc401.

FIG. 13is a flowchart of step2600ofFIG. 12. Referring toFIG. 13, in step2601, the MCU406counts a number of times the track-related signal is output, accumulates count values, and outputs the result as a first count value CNT1. In step2602, the MCU406determines whether the first count value CNT1is equal to a first set value. If, in step2602, it is determined that the first count value CNT1is equal to the first set value, in step2603, the MCU406counts a number of times the track-related signal is output, accumulates count values, and outputs the result as a second count value CNT2.

Here, to be more specific, when the track-related signal is high, the MCU406counts up the number of times the track-related signal is output, but when the track-related signal is low, the MCU406counts down the number of times the track-related signal is output. The second count value CNT2can be expressed with data having a predetermined number of bits, for example, 16-bit data of “16′h0000”. If a most significant bit of 16-bit data “0000˜FFFF” is inverted, the 16-bit data is changed into “8000˜0000˜7FFF”. Thus, when the second count value CNT2is represented with 16-bit data, the second count value CNT2may be “8000˜0000˜7FFF”.

Here, the MCU406, when counting down, counts from “0000” to “8000” and holds the count when the count is “8000”, and when counting normally, the MCU406counts from “0000” to “7FFF” and holds the count when the count is “7FFF”. Accordingly, when the number of times the counting up operation is performed is greater than the number of times the counting down operation is performed, the second count value CNT2has a most significant bit of “1”. In contrast, when the number of times the counting down operation is performed is greater than the number of times the counting up operation is performed, the second count value CNT2has a most significant bit of “0”. Here, the most significant bit serves as a sign bit.

In step2604, the MCU406determines whether a limit check time starts.

If, in step2604, it is determined that the limit check time starts, in step2605, the MCU406determines whether the sign bit of the second count value CNT2is “1”.

If, in step2605, it is determined that the sign bit of the second count value CNT2is not “1”, in step2606, the MCU406initializes the second count value CNT2and returns to step2603.

If, in step2605, it is determined that the sign bit of the second count value CNT2is “1”, in step2607, the MCU406determines whether the second count value CNT2is less than the second set value. Here, the second set value may be a predetermined value with a most significant bit of “1”. If it is determined that the second count value CNT2is greater than or equal to the second set value, the MCU406returns to step2606. If it is determined that the second count value CNT2is less than the second set value, in step2608, the MCU406outputs the limit check completion signal SVCLT to the SSP405. The SSP405then stops the operations of the sled motor414and the tracking actuator.

As previously described with reference toFIG. 13, when the track-related signal is high, the MCU406counts up the number of times the track-related signal is output. However, when the track-related signal is low, the MCU406counts down the number of times the track-related signal is output. Alternatively, the situation may be reversed such that when the track-related signal is high, the MCU406counts down, and when the track-related signal is low, the MCU406counts normally. In this case, the second set value may be a predetermined value with a most significant bit of “0”.

Accordingly, when the second count value CNT2has a most significant bit of “0” and is greater than the second set value, the MCU406determines that the optical pickup402has moved to the innermost perimeter of the optical disc401.

As previously described, in step2607, the MCU406compares the second count value CNT2with the second set value. However, in an alternative exemplary embodiment to that shown inFIG. 13, in step2607, the MCU406may measure a time for which the sign bit of the second count value CNT2remains at “1”. In more detail, if it is determined in step2605that the second count value CNT2has the sign bit of “1”, the MCU406may determine whether it remains at “1” for a predetermined period of time. When the sign bit of the second count value CNT2changes into “0” within the predetermined period of time, the MCU406initializes the second count value CNT2and returns to step2603. When the sign bit of the second count value CNT2remains at “1” for the predetermined period of time, in step2608, the MCU406outputs the limit check completion signal SVCTL to the SSP405. The SSP405then stops the operations of the sled motor414and the tracking actuator.

As described above, in an optical disc system and method for controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information, according to the exemplary embodiments of the present invention, time required for reading TOC information can be reduced. Also, the movement of the optical pickup to the innermost perimeter of the optical disc can be accurately controlled.

Moreover, the optical pickup can be controlled to move to an innermost perimeter of a disc on which data is recorded only in a portion of an inner area or of a blank disc on which data is not recorded.

Furthermore, even when only a focus servo is driven, the optical disc system can control the optical pickup to move to the innermost perimeter of the optical disc.