Optical disc drive with a system behavior detection module

An optical disc drive includes a servo system and a system behavior detection module. The system behavior detection module includes a controller and a signal feeding unit coupled to the controller and the servo system. The controller is operable in a detection mode and in a normal operation mode. In the detection mode, the controller enables the signal feeding unit so as to introduce an exciting signal into the servo system. In the normal operation mode, the controller disables the signal feeding unit so as to inhibit introduction of the exciting signal into the servo system.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese application no. 092131099, filed on Nov. 6, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an optical disc drive, more particularly to an optical disc drive with a system behavior detection module.

2. Description of the Related Art

As illustrated inFIGS. 1 and 2, a conventional optical disc drive comprises a servo system that includes an optical pickup unit11, an amplifier (or pre-amplifier)12coupled to the optical pickup unit11, a compensator13coupled to the amplifier12, and a driver unit14coupled to the optical pickup unit11and the compensator13.

The conventional optical disc drive further includes a controller chip (not shown). The amplifier12and the compensator13are normally built into the controller chip.

In operation, the optical pickup unit11emits light that is reflected by an optical disc (not shown). The reflected light is detected by the optical pickup unit11, which responds by providing a detected signal (DS) corresponding to the reflected light. The amplifier12receives the detected signal (DS) and provides an error signal (ES), such as a track error or focus error signal, corresponding to the detected signal (DS). The compensator13receives the error signal (ES) and a reference signal (RS), and provides a control signal (CS) corresponding to the error signal (ES) and the reference signal (RS). The driver unit14receives the control signal (CS) and drives movement of the optical pickup unit11, i.e., movement of an object lens (not shown) of the optical pickup unit11, in accordance to the control signal (CS), thereby resulting in correction of the focusing and tracking of the light emitted by the optical pickup unit11.

In order for the driver unit14to drive movement of the optical pickup unit11so that the light emitted by the optical pickup unit11can be accurately focused on the tracks on the optical disc, the compensator13must be designed based on the behavior of the servo system during the development stage of the optical disc drive.

A conventional method for detecting the behavior of the servo system comprises the following steps of cutting the electrical connection between the compensator13and the driver unit14, connecting an adder circuit15between the compensator13and the driver unit14, using a dynamic system analyzer20to introduce an exciting signal (XS), such as a variable frequency sinusoidal signal, into the servo system through the adder circuit15, using the system analyzer20to obtain output and input signals from a junction161of the compensator13and the adder circuit15, and a junction162of the adder circuit15and the driver unit14, and using the system analyzer20to calculate gain and phase relationships between the input and output signals. The gain and phase relationships calculated by the system analyzer20can then be used as parameters in designing the compensator13.

Although the above-mentioned method achieves the purpose of detecting the behavior of the servo system, the alteration of the circuitry of the servo system to connect the adder circuit15may arise in interference to the exciting signal (XS). As a result, the resulting calculation of the gain and phase relationships may not be accurate. Furthermore, the system analyzer20is not economically practical for this purpose due to its high cost.

SUMMARY OF THE INVENTION

Therefore, the main object of the present invention is to provide an optical disc drive with a built-in system behavior detection module.

Another object of the invention is to provide a system behavior detection module for an optical disc drive.

According to one aspect of the present invention, an optical disc drive comprises a servo system and a system behavior detection module. The servo system includes an optical pickup unit for generating a detected signal, an amplifier coupled to the optical pickup unit for generating an error signal associated with the detected signal, a compensator for processing the error signal to result in a control signal, and a driver unit coupled to the optical pickup unit and responsive to the control signal for position correction of the optical pickup unit. The system behavior detection module includes a controller and a signal feeding unit coupled to the controller and the servo system. The controller is operable in a detection mode. In this mode, the controller enables the signal feeding unit so as to introduce an exciting signal into the servo system. The controller is further operable in a normal operation mode. In this mode, the controller disables the signal feeding unit so as to inhibit introduction of the exciting signal into the servo system.

According to another aspect of the present invention, a system behavior detection module for an optical disc drive comprises a controller and a signal feeding unit. The optical disc drive has a servo system that includes an optical pickup unit for generating a detected signal, an amplifier coupled to the optical pickup unit for generating an error signal associated with the detected signal, a compensator for processing the error signal to result in a control signal, and a driver unit coupled to the optical pickup unit and responsive to the control signal for position correction of the optical pickup unit. The signal feeding unit is coupled to the controller and is adapted to be coupled to the servo system. The controller is operable in a detection mode. In this mode, the controller enables the signal feeding unit so as to introduce an exciting signal into the servo system. The controller is further operable in a normal operation mode. In this mode, the controller disables the signal feeding unit so as to inhibit introduction of the exciting signal into the servo system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 3, the preferred embodiment of an optical disc drive according to this invention is shown to include a servo system3and a system behavior detection module4. It is noted herein that the optical disc drive actually includes other known components, such as a spindle motor, decoders, etc., not illustrated herein for the sake of simplicity.

The servo system3is conventional in construction, and includes an optical pickup unit31, an amplifier (or pre-amplifier)32coupled to the optical pickup unit31, a compensator33, and a driver unit34coupled to the optical pickup unit31and the compensator33.

In this embodiment, the system behavior detection module4includes a controller41and a signal feeding unit42. The signal feeding unit42is coupled to the controller41and the servo system3. In particular, the signal feeding unit42is coupled to and is disposed between the amplifier32and the compensator33. More particularly, the signal feeding unit42includes adder and switch circuits421,422, and has a control input423connected electrically to the controller41. The adder circuit421has a first input4211coupled to the amplifier32, a second input4212for receiving an exciting signal (XS), and an output4213coupled to the compensator33. The switch circuit422has a first terminal4221, and a second terminal4222coupled to the second input4212of the adder circuit421.

Although the signal feeding unit42of this embodiment is coupled to and is disposed between the amplifier32and the compensator33, it should be apparent to those skilled in the art that the signal feeding unit42may be coupled to and disposed anywhere in the servo system3as long as the exciting signal (XS) can be introduced into the servo system3when the controller41operates in a detection mode (to be described hereinafter). For example, the signal feeding unit42may be coupled to and disposed between the compensator33and the driving unit34.

It is noted that the exciting signal (XS) is a sinusoidal waveform, the parameters (e.g. frequency, offset voltage, amplitude, etc.) of which are set by the user.

The system behavior detection module4further includes a signal generator46coupled to the signal feeding unit42and the controller41. In particular, the signal generator46has an output461connected electrically to the first terminal4221of the switch circuit422, and a control input462connected electrically to the controller41.

In this embodiment, the controller41is operable in a normal operation mode and in a detection mode. In the normal operation mode, the controller41controls the switch circuit422such that the first terminal4221is disconnected from the second terminal4222so as to disable receipt of the exciting signal (XS) by the adder circuit421. As a result, the adder circuit421of the signal feeding unit42is inhibited from introducing the exciting signal (XS) into the servo system3. Preferably, the controller41disables the signal generator46so as to inhibit provision of the exciting signal (XS) to the signal feeding unit42. As a consequence, during operation of the optical disc drive, the optical pickup unit31emits light, processes light reflected from an optical disc (not shown), and generates a detected signal (DS) corresponding to the reflected light. The amplifier32then generates an error signal (ES) associated with the detected signal (DS) in a known manner. The adder circuit421of the signal feeding unit42receives and provides an intermediate signal (IS) corresponding to the error signal (ES). The compensator33receives the intermediate signal (IS) and a reference signal (RS), and processes the intermediate signal (IS) and the reference signal to result in a control signal (CS) corresponding to the error signal (ES) and the reference signal (RS). The driver unit34is responsive to the control signal (CS) for position correction of the optical pickup unit31in a known manner.

In the detection mode, the controller41enables the signal generator46so as to provide the exciting signal (XS) to the signal feeding unit42, and controls the switch circuit422such that the first terminal4221is connected to the second terminal4222so as to enable receipt of the exciting signal (XS) by the adder circuit421. At this time, the adder circuit421of the signal feeding unit42is able to introduce the exciting signal (XS) into the servo system3. As a consequence, during operation of the optical disc drive, the adder circuit421of the signal feeding unit42receives both the error and exciting signals (ES, XS), introduces the exciting signal (XS) into the error signal (ES), and provides an intermediate signal (IS′) corresponding to the exciting and error signals (XS, ES).

The system behavior detection module4further includes a calculating circuit44coupled to the servo system3and the controller41. In this embodiment, the calculating circuit44is controlled by the controller41so as to capture input and output signals in the servo system3, and so as to calculate gain and phase relationships between the input and output signals when the controller41operates in the detection mode. In particular, the calculating circuit44includes gain and phase calculating units441,442, and has a control input443connected electrically to the controller41. Each of the gain and phase calculating units441,442has an input side4411,4421coupled to the servo system3, and an output side4412,4422. The gain calculating unit441calculates the gain relationship between the input and output signals, whereas the phase calculating unit442calculates the phase relationship between the input and output signals.

In this embodiment, each of the input and output signals is obtained from one of a first junction361of the amplifier32and the signal feeding unit42, a second junction362of the signal feeding unit42and the compensator33, and a third junction363of the compensator33and the driver unit34. It is noted that the input and output signals must be obtained from two different junctions361,362,363at any given time.

The system behavior detection module4further includes a selector circuit43coupled to the servo system3and the controller41. In this embodiment, the selector circuit43is controlled by the controller41so as to obtain the input and output signals from selected ones of the first, second and third junctions361,362,363, and so as to provide the input and output signals to the calculating circuit44when the controller41operates in the detection mode. In particular, the selector circuit43includes first and second selecting members431,432, and has a control input433connected electrically to the controller41. Each of the first and second selecting members431,432has an input side4311,4321connected electrically to the first, second and third junctions361,362,363, and an output side4312,4322connected electrically to the input side4411,4421of a respective one of the gain and phase calculating units441,442of the calculating circuit44. The first selecting member431of the selector circuit43provides the input signal to each of the gain and phase calculating units441,442of the calculating circuit44, whereas the second selecting member432provides the output signal to each of the gain and phase calculating units441,442of the calculating circuit44.

The system behavior detection module4further includes a memory device45coupled to the calculating circuit44and the controller41. In this embodiment, the memory device45is controlled by the controller41so as to store the gain and phase relationships calculated by the calculating circuit44when the controller41operates in the detection mode. Preferably, the memory device41is a dynamic random access memory (DRAM).

In this embodiment, the system behavior detection module4is incorporated together with the amplifier32and the compensator33in a single integrated controller chip. It is noted that a computing device (not shown) may be externally connected to the controller chip to extract the stored calculated gain and phase relationships for performing behavioral analysis of the servo system3.

In an alternative embodiment, the signal generator46is dispensed with. The controller chip is provided with an input pin coupled to the first terminal4221of the switch circuit422. An external signal generator (not shown) is connected to the input pin of the controller chip for providing the exciting signal (XS) when the controller41operates in the detection mode.

In yet another alternative embodiment, the selector circuit43, the calculating circuit44, and the memory device45are dispensed with. The controller chip is provided with first, second and third output pins coupled to the first, second and third junctions361,362,363, respectively. An external calculating device (not shown) is connected to the first, second and third output pins for calculating the gain and phase relationships between the selected input and output signals when the controller41operates in the detection mode.

It has thus been shown that the optical disc drive of this invention includes a servo system3and a system behavior detection module4. The servo system3includes a compensator33and an amplifier32. The system behavior detection module4includes a signal feeding unit42that is incorporated together with the compensator33and the amplifier32in a controller chip. As such, an exciting signal (XS) can be conveniently introduced into the servo system3without the problem of interference during behavior detection. Moreover, the system behavior detection module4further includes a calculating circuit44for capturing input and output signals and for calculating gain and phase relationships between the input and output signals, and a memory device45for storing the calculated gain and phase relationships. By simply connecting an external computing device to the controller chip, the calculated gain and phase relationships can be extracted for further analysis. As such, there is no need for an expensive system analyzer. Further, since the controller chip per se already includes the selector circuit43, the calculating circuit44, the memory device45, and the signal generator46, the system behavior detection module4can be implemented in an existing servo system by mere addition of the signal feeding unit42. As such, the system behavior detection module4can be implemented at a relatively low cost.