KR19980078519A - Method and apparatus for detecting focusing of optical disc player - Google Patents

Abstract

end. The technical field to which the invention described in the claims belongs

A method and apparatus for detecting a focusing state of an optical pickup in an optical disc reproducing apparatus.

I. The technical problem to be solved by the invention

Provided are a focusing detection method and apparatus for simplifying a hardware configuration.

All. Summary of Solution of the Invention

The envelope level detected from the RF amplifier with respect to the RF signal generated from the optical pickup is compared with the offset level preset by the digital servo signal processor to detect the focus on state when the envelope level is larger than the offset level.

la. Important uses of the invention

It is used in an optical disk player.

Description

Method and apparatus for detecting focusing of optical disc player

TECHNICAL FIELD The present invention relates to an optical disc reproducing apparatus, and more particularly, to a method and apparatus for detecting a focusing state of an optical pickup.

Currently, optical disc playback devices that reproduce signals from discs such as compact discs (CDs), compact discs (compact discs-read only memory), LDs (laser discs), MDs (Mini Discs), DVDs (Digital Video Discs), etc. It is widely used. In such an optical disc reproducing apparatus, a signal recorded on a disc is output as an RF (Radio Frequency) signal optically picked up by an optical pickup and converted into an electrical signal. At this time, in order to pick up the signal from the disc, the focus of the optical pickup to the disc must be ON. Accordingly, the servo signal processing unit of the optical disk reproducing apparatus first starts the focusing servo control for the optical pickup and then checks the focusing state and starts various servo control for signal reproduction after the focus is turned on. As the servo signal processor, a digital servo signal processor (hereinafter referred to as DSSP), which is usually provided as a single chip IC (Integrated Circuit), is used. As described above, in the optical disc reproducing apparatus, it is necessary to detect the focusing state of the optical pickup. For this purpose, the optical disc reproducing apparatus is provided with a focusing detection circuit.

Focusing detection circuits, which have been used previously, have been incorporated into RF amplifiers that amplify and waveform-shape the RF signals generated from optical pickups. A typical focusing detection circuit has detected a DC (Direct Current) level for an RF signal generated from an optical pickup and confirmed focusing conditions therefrom to generate a focus on signal (hereinafter referred to as an FOK signal) indicating whether focus is on. The FOK signal generated in this way is applied to the DSSP as described above and used for servo control.

On the other hand, as described above, since the focusing detection circuit is incorporated in the RF amplifier, the configuration of the RF amplifier has become more complicated. In addition, a separate line was needed to transmit the FOK signal between the RF amplifier and the DSSP.

As described above, since the focusing detection circuit is built in the RF amplifier, the configuration of the RF amplifier is complicated and there is a problem that a line for transmitting the FOK signal between the RF amplifier and the DSSP is required.

Accordingly, an object of the present invention is to provide a focusing detection method and apparatus that can simplify the hardware configuration.

1 is a schematic block diagram of a conventional optical disc player;

2 is a circuit diagram showing an example of a conventional focusing detection device;

3 is a block diagram of an optical disc reproducing apparatus according to an embodiment of the present invention;

4 is a process flow diagram of a DSSP according to an embodiment of the present invention;

5 is an operational waveform diagram of the present invention.

In order to achieve the above object, the present invention compares an envelope level detected from an RF amplifier with respect to an RF signal generated from an optical pickup, and compares the envelope level with an offset level preset by the digital servo signal processor. It is characterized in that the detection in the focus-on state when the level is greater than the level.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Many specific details are set forth in the following description and in the accompanying drawings to provide a more general understanding of the invention. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. And a detailed description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted. In addition, it should be noted that in the following description, the same components in the drawings represent the same reference signs wherever possible.

1 shows a schematic block diagram of a conventional optical disc reproducing apparatus. In FIG. 1, the optical pickup 102 optically picks up the information recorded on the disk, generates an RF signal converted into an electrical signal, and outputs the RF signal to the RF amplifier 108. This optical pickup 102 is driven by a focusing actuator for a focusing servo and a tracking actuator for a tracking servo. Tracking servo refers to following the optical pickup 102 to a track on the disk 100, and focusing servo refers to keeping the optical pickup 102 for the disk 100 in focus on. The spindle motor 104 is driven by the control of the DSSP 114 to rotate the disk 100 at a constant linear velocity (CLV). A sled feed motor 106 is driven by sled feed servo control of the DSSP 114 to feed the optical pickup 102 in the radial direction on the disk 100.

In addition, the RF amplifier 108 amplifies and waveform-forms an RF signal applied from the optical pickup 102 and applies the digital signal processor (DSP) 110 to generate signals for tracking servo and focusing servo to generate the DSSP 114. To apply. The DSP 110 demodulates the data from the waveform-formed signal applied from the RF amplifier 108 and corrects the data to the output processor 112. The output processor 112 processes the data output from the DSP 110 to generate a final output signal such as an audio signal. The DSSP 114 is controlled by the CPU 116 and directed to the focusing servo and tracking servo, sled feed motor 106 for the optical pickup 102 in accordance with signals applied from the RF amplifier 108 and the DSP 110. For the sled feed servo, for the spindle motor 104, and the like. The CPU 116 is a main control unit of the optical disc player, and performs overall control for performing various functions of the optical disc player.

FIG. 2 is a circuit diagram showing an example of a focusing detection circuit built in the RF amplifier 108 as described above in the above optical disk reproducing apparatus. The focusing detection circuit of FIG. 2 passes the RF signal generated from the optical pickup 102 of FIG. 1 through the capacitor 200 and subtracts the difference between the signals RFi and RFo that appear at both ends of the capacitor 200, respectively. Is detected by The RFi signal is an RF signal applied from the optical pickup 102 and input to the capacitor 200, and the RFo signal is an RF signal output through the capacitor 200. Accordingly, the output of the subtractor 202 becomes the DC level of the RF signal. As such, the DC level output from the subtractor 202 is proportional to the amount of reflected light reflected from the disk 100 to the optical pickup 102.

This DC level is applied to the comparator 204 and compared with a preset offset level, and the output of the comparator 204 becomes the FOK signal as described above. At this time, the offset level is a reference level for detecting the focus on state of the optical pickup 102 with respect to the disc 100. If the optical pickup 102 is in the focus-on state, the DC level becomes larger than the offset level, and the FOK signal is output at a high level. On the other hand, if the optical pickup 102 is not in the focus-on state, since there is no reflected light from the disk 100 or the amount of reflected light is relatively small, the DC level becomes smaller than the offset level, and the FOK signal becomes a low level. Accordingly, as shown in FIG. 1, the DSSP 114 inputting the FOK signal from the RF amplifier 108 can confirm the focusing state of the optical pickup 102 by the FOK signal.

However, since the focusing detection circuit as described above is incorporated in the RF amplifier 108 as described above, the configuration of the RF amplifier 108 is complicated, and the FOK signal is transmitted between the RF amplifier 108 and the DSSP 114. A line was needed to transmit.

To improve this, the present invention detects the focusing state of the optical pickup 102 without embedding a separate focusing detection circuit in the RF amplifier 108.

Figure 3 shows a block diagram of an optical disc reproducing apparatus to which the present invention is applied, and the configuration and operation of portions except for the RF amplifier 300 and DSSP 302 are the same as those of the optical disc reproducing apparatus of FIG. . The RF amplifier 300 and the DSSP 302 correspond to the RF amplifier 108 and the DSSP 114 of FIG. 1, respectively. However, unlike the RF amplifier 108, the RF amplifier 300 does not have a focusing detection circuit, and the DSSP 302, unlike the DSSP 114, additionally performs a function according to the processing flowchart shown in FIG. Accordingly, reference numerals for the RF amplifier 300 and the DSSP 302 of FIG. 3 are different from those of FIG. 1, and the remaining functions of the RF amplifier 300 and the DSSP 302 are the same as those of FIG. 1.

Also, the envelope signal ENV, the laser diode on signal LD_ON, and the laser control signal LASER_CTL shown in FIG. 3 are signals generated in a conventional optical disc reproducing apparatus. Although these signals are omitted in FIG. 1, they are shown in FIG. 3 because they are related to the present invention. First, the ENV signal applied from the RF amplifier 300 to the DSSP 302 is an envelope for the RF signal generated from the optical pickup 102. As usual, the RF amplifier 300 detects an envelope for the RF signal and outputs the envelope to the DSSP 302. The reason for detecting the envelope in the RF amplifier 300 as described above is to allow the DSSP 302 to check the level of the RF signal. This envelope is proportional to the amount of reflected light reflected from the disk 100 to the optical pickup 102 in the same manner as the DC level detected by the subtractor 202 in the focusing detection circuit of FIG. 2 described above. The laser diode on signal LD_ON applied from the DSSP 302 to the RF amplifier 300 is a signal for turning on the laser output of the optical pickup 102, and the RF amplifier 300 inputs the laser diode on signal LD_ON activated. Is turned on by the laser control signal LASER_CTL.

4 is a flowchart illustrating a process of the DSSP 302 according to an exemplary embodiment of the present invention. A process of detecting an envelope signal ENV level in a focus-on state when the envelope signal ENV level is larger than the offset level is compared with a preset offset level. Will be shown. Functions according to the process flow diagram of FIG. 4 are programmed into the DSSP 302. The operation according to the flowchart of FIG. 4 is performed in the DSSP 302 under the control of the CPU 116 when the signal playback from the disc 100 is to be started in the optical disc reproducing apparatus of FIG. 3 described above. An operating waveform diagram of 3 is shown in FIG. 5. First, the DSSP 302 activates the laser diode ON signal LD_ON high in step 400 of FIG. 4. The laser output of the optical pickup 102 is then turned on by the RF amplifier 300. The time point at this time is shown in FIG.

In this state, the DSSP 302 starts focusing servo control in step 402 to move the optical pickup 102 toward the disc 100 by the focus actuator. Then, the amount of light reflected from the disk 100 appears so that the RF signal is output from the optical pickup 102. As the envelope for the RF signal is detected by the RF amplifier 300, the envelope signal ENV appears as shown in FIG. This time point is shown in FIG. 5 as the time point t1. The level of such an envelope signal ENV is gradually increased as shown in FIG. When the envelope signal ENV level starts to be detected at the time t1 of FIG. 5, does the DSSP 302 compare the level of the envelope signal ENV with the offset level set as in the example of FIG. 5 in step 406 to be greater than the offset level? Check it. In this case, when the envelope level becomes larger than the offset level as in the time t2 of FIG. 5, the DSSP 302 detects the focus on state in step 408.

Therefore, the focusing state can be detected in the DSSP 302 using the envelope level that is typically generated in the RF amplifier 300 without having a separate focusing detection circuit embedded in the RF amplifier 300.

On the other hand, after confirming the focus on state as described above, the DSSP 302 starts the normal servo control as described above with respect to the optical pickup 102.

As described above, the present invention does not need to separately include a focusing detection circuit in the RF amplifier by detecting focusing using an envelope for the RF signal, and also does not need a line for transmitting FOK between the RF amplifier and the DSSP. There is an advantage to simplifying this.

Claims (3)

In the focus detection method of the optical disk player, Focusing on an RF signal generated from an optical pickup by comparing the envelope level detected from the RF amplifier with a preset offset level in the digital servo signal processing unit and detecting the focus level when the envelope level is greater than the offset level. Detection method. In the focusing detection device of the optical disk player, An optical pickup that optically picks up the information recorded on the disk and generates an RF signal converted into an electrical signal; An RF amplifier for amplifying and waveform-shaping the RF signal and outputting the same while detecting and outputting an envelope of the RF signal; And a digital servo signal processor configured to detect the envelope level as a focus-on state when the envelope level is greater than the offset level and compare the envelope level with a preset offset level, and perform servo control on the optical pickup for reproducing a signal from the disk. Focusing detection device. The focusing detection method of claim 2, wherein the digital servo signal processing unit compares the envelope level with the offset level while turning on the laser output of the optical pickup through the RF amplifier and starting focusing servo control. Device.