KR100220702B1 - Focusing servo of digital video disc recorder system - Google Patents

Abstract

The present invention relates to a focusing servo device of a DVDR system which drives and controls an optical pickup unit such that a signal surface of the optical disc is located within a focal depth of the laser beam of the optical pickup unit by using a focusing error signal detected corresponding to the amount of light reflected from the optical disk. A comparison unit comparing the focusing error signal with a preset error compensation range and generating a signal corresponding thereto; A switch for switching off and blocking the focusing error signal when the focusing error signal is out of a predetermined error compensation range as a result of the comparison by the comparison unit; The capacitor is charged with a voltage while the switch is in an on state, and further comprises a capacitor for discharging the charged voltage in the switch-on state when the switch is turned off. There is an effect to improve the reliability of the DVDR system by controlling to remain within the compensation range.

Description

Focusing Servo Device of DVD System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing servo device of a digital video disc recorder system. In particular, a focusing servo of a DVDR system capable of controlling the focusing error signal to be within the error compensation range capable of compensating for the focusing error is provided. It is about.

In general, optical discs are read-only type in which the user can only play the information according to its function and purpose, and additional recording type and repetitive recording of information that the user can record once and read the recorded information many times but cannot erase and re-record It can be divided into erasing rewritable type that can be erased and reproduced. Among such optical discs, a system capable of recording, erasing and playing on an erasable rewritable optical disc is commonly referred to as a DVDR system.

On the other hand, when recording, erasing, and reproducing certain data on such an erased rewritable optical disc, in order for the optical pickup unit of the DVDR system to accurately record, erase, and reproduce data on the optical disc, the signal surface of the optical disc is within the depth of focus of the laser beam of the optical pickup unit. Adjust to position In this way, adjusting the signal surface of the optical disk to be located within a certain depth of focus of the laser beam of the optical pickup is called a focusing servo, and such focusing servo is performed by a focusing servo device.

A description will now be given of an operation process of a general focusing servo device, which is widely known.

1 is a block diagram illustrating a focusing servo device of a DVDR system according to the related art, including a photodetector 100, a first current-voltage converter 210, a second current-voltage converter 220, The error detector 300, the difference compensator 400, and the driver 500 may be provided.

First, the photo detector 100 is composed of four photo diodes (D1, D2, D3, D4) divided into four, and is reflected from the optical disk through each photo diode (D1, D2, D3, D4). Light is detected and a current corresponding to the detected light is generated.

The first current-voltage converter 210 and the second current-voltage converter 220 are composed of two sets of OP amplifiers, and such an OP amplifier has a resistance at its inverting input stage, as shown in a detailed circuit diagram in FIG. (R1), the non-inverting input terminal is grounded, and a feedback loop having a loop resistance (Rf) is formed from the output terminal to the inverting input terminal.

The first current-to-voltage converter 210 configured as described above adds currents generated from the pair of diodes D2 and D4 located in the diagonal direction of the quadrant photodetector 100, respectively, and adds the currents. Is converted into a constant voltage, and the converted voltage is provided to one input terminal of the error detector 300.

In addition, the second current-voltage converter 220 also adds the currents generated by the pair of diodes D1 and D3 positioned in the diagonal direction of the quadrature photodetector 100, respectively, and adds the currents. Is converted into a constant voltage, and the converted voltage is provided to another input terminal of the error detector 300.

At this time, the voltage provided from the current-voltage converters 210 and 220 is output as a product of the loop resistance Rf with respect to the addition current I generated by the pair of diodes, and the phase is inverted. That is, the output voltage is output as -I * Rf.

The error detector 300 amplifies the difference between the two input voltages when the voltages provided by the two sets of current-voltage converters 210 and 220 are input to the two input terminals of the error detector 300, respectively. In this case, the generated voltage is a focusing error signal, and represents a degree in which a signal surface of the optical disk deviates from a predetermined depth of focus of the laser beam provided in the optical pickup unit.

The phase compensator 400 compensates for the phase of the focusing error signal generated by the error detector 300, amplifies the signal, and outputs the amplified signal as a drive control signal for driving the driver 500.

The driving unit 500 generates a driving signal for driving the focusing actuator coil by the driving control signal output from the phase compensator 400, and the focusing actuator coil is driven by the driving signal generated by the driving unit 500.

The objective lens is moved up and down by driving the actuator coil, and the signal surface of the optical disc is adjusted to be located within a certain depth of focus of the laser beam by the movement of the objective lens.

However, in the focusing servo device of the DVDR system according to the related art as described above, as indicated by T1 and T2 in FIG. 2 due to scratches, fingerprints, block dots, or external shocks on the optical disc. When the focusing error signal is out of the error compensation range, that is, the maximum value (Emax) or the minimum value (Emin) of the error compensation range capable of compensating the focusing error signal, the signal surface of the optical disc has the depth of focus of the laser beam of the optical pickup section. There was a problem that was difficult to adjust to be located within.

Accordingly, an object of the present invention is to provide a focusing servo device of a DVDR system in which a focusing error signal can be maintained within a predetermined error compensation range in a DVDR system. There is.

In order to achieve the above object, in the present invention, by using the focusing error signal detected corresponding to the amount of light reflected from the optical disk, driving control of the optical pickup so that the signal surface of the optical disk is located within the focal depth of the laser beam of the optical pickup portion A focusing servo device of a DVDR system; A comparison unit comparing the focusing error signal with a preset error compensation range and generating a signal corresponding thereto; A switch for switching off and blocking the focusing error signal when the focusing error signal is out of a predetermined error compensation range as a result of the comparison by the comparison unit; And a capacitor which charges a voltage while the switch is in an on state, and discharges the charged voltage in the optical pickup unit when the switch is switched off. Provides a focusing servo device.

1 is a block diagram showing a focusing servo device of a DVDR system according to the prior art;

2 is a waveform diagram showing a focusing error signal in the focusing servo device of the DVDR system;

3 is a circuit diagram illustrating a focusing servo device of a DVDR system according to an embodiment of the present invention;

4 is a circuit diagram illustrating a focusing servo device of a DVDR system according to another embodiment of the present invention;

5 is a waveform diagram showing a focusing error signal in the focusing servo device of the DVDR system according to the present invention;

* Explanation of symbols for main parts of the drawings

Reference numeral 100 is a photodetector 210: a first current-voltage converter.

220: second current-voltage converter 300: error detector

400: phase compensator 500: driver

610: first comparator 620: second comparator

630: OR gate C :: capacitor

SW1, SW2, SW: Switch

R1, R2: resistance

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

3 is a circuit diagram illustrating a focusing servo device of a DVDR system according to an embodiment of the present invention, and FIG. 4 is a circuit diagram illustrating a focusing servo device of a DVDR system according to another embodiment of the present invention. Hereinafter, with reference to the waveform of the focusing error signal according to the prior art shown in Figure 2 and the waveform of the focusing error signal according to the present invention shown in Figure 5, DVDR system according to an embodiment of the present invention and another embodiment The operation process of the focusing servo device will be described sequentially.

In addition, for the sake of understanding, the same reference numerals will be used for the same members as those of the focusing servo device of the DVDR system according to the prior art.

First, a focusing servo device of a DVDR system according to an embodiment of the present invention includes a first comparator 610 which compares a focusing servo device of a DVDR system according to the prior art with a focusing error signal greater than a maximum value of an error compensation range. And a second comparator 620 for comparing whether a focusing error signal is smaller than a minimum value of the error compensation range, a first switch SW1 corresponding to a comparison result of the first comparator 610, and a second comparator. When the second switch SW2 and the first switch SW1 or the second switch SW2 that are correspondingly switched according to the comparison result of 620 are turned off, the first switch SW1 and the second switch. Capacitor C for discharging the charged voltage while maintaining (SW2) is characterized in that it further comprises.

Operation of the focusing servo device of the DVDR system according to an embodiment of the present invention, characterized in that the configuration member is as follows.

First, the focusing error signal detected via the photodetector 100, the first current-voltage converter 210, the second current-voltage converter 220, and the error detector 300 is a first comparator 610. ) And an inverting terminal of the second comparator 620.

The first comparator 610 is composed of two input terminals and one output terminal, and compares the signals inputted to the two input terminals, and outputs high and low logic signals in response to the comparison result. It is composed. In this case, the focusing error signal output from the error detector 300 is input to the non-inverting input terminal (+) of the first comparator 610, and the maximum value Emax of the preset error compensation range is input to the inverting input terminal (-). Is input, and its output is provided to the first switch SW1.

That is, if the focusing error signal is greater than the maximum value of the error compensation range, a high (H) signal is output, and if the focusing error signal is less than the maximum value of the error compensation range, a low (L) signal is output.

One end of the first switch SW1 is connected to the error detector 300, and the other end thereof is connected to the second switch SW2, and is switched in response to the output value of the first comparator 610. That is, while the ON state is maintained while the low L signal is output from the first comparator 610, and the high H signal is output from the first comparator 610, the first switch SW1 is used. Is switched off.

On the other hand, the second comparator 620 is also composed of two input terminals and one output terminal, OP to compare the signal applied to the two input terminals, and outputs a logic signal of high and low in response to the comparison result It consists of an amplifier. At this time, the focusing error signal output from the error detector 300 is input to the inverting input terminal (-) of the second comparator 620, and the minimum value Emin of the preset error compensation range is input to the non-inverting input terminal (+). Input, and its output is provided to the second switch SW2.

That is, when the focusing error signal is smaller than the minimum value of the error compensation range, a high (H) signal is output. When the focusing error signal is greater than the minimum value of the error compensation range, a low (L) signal is output.

One end of the second switch SW2 is connected to the second switch SW2, the other end thereof is connected to the capacitor C in parallel, and is switched in correspondence with the output value of the second comparator 620. That is, when the signal output from the second comparator 620 is low (L), the second switch SW2 is kept in an on state, and the signal output from the second comparator 620 is high (H). ), The second switch SW2 is switched off.

In order to understand the operation of the first comparator 610 and the second comparator 620 described above, referring to the focusing error signal illustrated in FIG. 2, the focusing error signal output from the error detector 300 is an error. In the section T1 that is larger than the maximum value Emax of the compensation range, the first switch SW1 is turned off, and the section in which the focusing error signal output from the error detector 300 becomes smaller than the minimum value Emin of the error compensation range ( In T2), the second switch SW2 is turned off.

Here, since the first switch SW1 and the second switch SW2 are connected in series, even if only one of the two switches SW1 and SW2 is turned off, the first switch SW1 and the second switch SW2 are outputted from the error detector 300 so as to output the phase compensator 400. The focusing error signal provided at) will be blocked.

When the focusing error signal output from the error detector 300 is blocked, the capacitor C will discharge the charged voltage while the first switch SW1 and the second switch SW2 are in an on state. The focusing error signal will decrease or increase exponentially and fall within the error compensation range.

That is, as shown in FIG. 5, in the section in which the focusing error signal is out of the error compensation range, the focusing error signal is exponentially reduced and positioned within the error compensation range by the voltage discharge of the capacitor C. FIG.

At this time, since the focusing error signal is within the error compensation range, the first comparator 610 and the second comparator 620 output a low L signal, whereby the first switch SW1 and the second switch SW. Since the on state is maintained, the focusing error signal output from the error detector 300 is provided to the phase compensator 400.

The focusing error signal provided by the error detector 300 passes through the phase compensator 400 and the driver 500. When the focusing actuator coil is driven by this, the objective lens moves up and down by driving the actuator coil.

Thus, by the movement of the objective lens, the signal surface of the optical disc is adjusted to be located within a certain depth of focus of the laser beam.

The focusing servo device of the DVDR system according to another embodiment of the present invention is shown in FIG. 4, and as shown in the figure, in the focusing servo device of the DVDR system according to the prior art, a focusing error signal has a maximum error compensation range. The first comparator 610 for comparing the value greater than the value, the second comparator 620 for comparing the focusing error signal less than the minimum value of the error compensation range, and the first comparator 610 and the second comparator 620. When the OR gate 630 for ORing the output and the switch SW corresponding to the comparison result of the OR gate 630 and the switch SW are turned off to block the focusing error signal, the switch ( It further comprises a capacitor (C) for discharging the charged voltage when the SW is on (On) state.

Since the operation of the first comparator 610, the second comparator 620, and the capacitor C, which are the same as the focusing servo device of the DVDR system according to the embodiment of the present invention, has been described in detail above, Hereinafter, an operation process of the newly provided OR gate 630 and the switch SW according to another embodiment of the present invention will be described.

First, the focusing error signal detected via the photodetector 100, the first current-voltage converter 210, the second current-voltage converter 220, and the error detector 300 is a first comparator 610. ) Is compared with the maximum value Emax of the error compensation range, and the second comparator 620 is compared with the minimum value Emin of the error compensation range, and its respective output is provided to two inputs of the OR gate 630. .

The OR gate 630 performs an OR on the logic signals input from the first comparator 610 and the second comparator 620, respectively, and provides a result of the OR to the switch SW, and the switch SW is the OR gate 630. ) Is kept on while the low (L) signal is output, and is switched off when the high (H) signal is output from the OR gate 630.

That is, when both the first comparator 610 and the second comparator 620 output the low L signal, the OR gate 630 will output the low L signal, and the OR gate 630 will output the low L signal. When the L) signal is output, the switch SW is kept on.

At this time, the output of the low L signal from the OR gate 630 means that the focusing error signal output from the error detector 300 is maintained within the error compensation range, and the switch SW is turned on. Since the state is maintained, the focusing error signal passes through the phase compensator 400 and the driver 500. When the focusing actuator coil is driven by this, the objective lens is moved up and down by driving the actuator coil.

On the other hand, if any one of the first comparator 610 and the second comparator 620 outputs a high (H) signal, the OR gate 630 will output a high (H) signal, OR gate 630 When the high (H) signal is output, the switch SW will be switched from the on state to the off state.

Therefore, the focusing error signal output from the error detector 300 and provided to the phase compensator 400 may be blocked by the switch SW.

When the focusing error signal output from the error detector 300 is blocked, the capacitor C will discharge the charged voltage while the switch SW is on, and the focusing error signal is exponentially It will decrease or increase and fall within the error compensation range.

That is, the output of the high (H) signal from the OR gate 630 means that the focusing error signal output from the error detector 300 is outside the error compensation range, and thus the focusing error signal is the error compensation range. In the section deviating, the focus error error signal is exponentially reduced by the voltage discharge of the capacitor C so as to be positioned within the error compensation range.

As a result, since the focusing error signal is maintained within the error compensation range, the switch SW is turned on again, and when the switch SW is turned on, the focusing error signal is passed through the phase compensator 400 and the driver 500. When the focusing actuator coil is driven by this, the objective lens moves up and down by driving the actuator coil.

Thus, by the movement of the objective lens, the signal surface of the optical disc is adjusted to be located within a certain depth of focus of the laser beam.

As described above, according to the present invention, in a focusing servo of a DVDR system, if a focusing error signal that is out of a predetermined error compensation range is generated, the focusing error signal is blocked, and then the voltage charged in the capacitor is exponentially charged. By slowly discharging, the focusing error signal is kept within a predetermined error compensation range, thereby stably performing the focusing servo operation of the DVCR, thereby improving the reliability of the DVDR system.

Claims (4)

A focusing servo device of a DVDR system for driving and controlling an optical pickup unit such that a signal surface of the optical disc is located within a focal depth of the laser beam of the optical pickup unit by using a focusing error signal detected corresponding to the amount of light reflected from the optical disk. A comparator for comparing the focusing error signal with a preset error compensation range and generating a signal corresponding thereto; A switch for switching off the focusing error signal when the focusing error signal is out of a predetermined error compensation range as a result of the comparison by the comparison unit; And a capacitor which charges a voltage while the switch is in the on state, and discharges the charged voltage to the optical pickup unit when the switch is turned off. Focusing servo device in the system. The method of claim 1, wherein the comparison unit, A first comparator for turning off the switch when a maximum value of the focus error signal and a preset error compensation range is exceeded; And a second comparator for turning off the switch when the focus error signal is lower than a minimum value of a predetermined error compensation range. The method of claim 2, wherein the switch, A first switch switched off when a focusing error signal is greater than a maximum value of a preset error compensation range as a result of the comparison of the first comparator; And a second switch that is switched off when a focusing error signal is smaller than a minimum value of a preset error compensation range as a result of the comparison of the second comparator. The method of claim 1, wherein the comparison unit, A first comparing unit comparing the focus error signal with a maximum value of a preset error compensation range and generating a signal corresponding thereto; A second comparison unit comparing the focus error signal with a minimum value of a preset error compensation range and generating a signal corresponding thereto; And an OR gate that turns on / off the switch by ORing the outputs of the first and second comparators.

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