KR100209158B1 - Focus bias control apparatus - Google Patents

Abstract

The present invention relates to an apparatus for adjusting a focus bias of a DVDR system for driving an optical disc capable of recording, erasing, and reproducing, comprising: an optical pickup unit 110 for reading and outputting an RF signal from an optical disc; An A / D converter 120 for converting the RF signal read by the optical pickup unit into a digital signal and outputting the digital signal; A focus bias adjuster 130 for adjusting a focus bias voltage of the optical pickup 110; A focus error signal generator 140 generating a focus error signal corresponding to the focus error of the optical pickup 110; A focus servo unit 150 for adjusting the focus of the optical pickup unit 110 by using the focus error signal generated by the focus error signal generator 140 and the focus bias voltage; Sequentially providing a plurality of preset bias voltages to the focus bias adjuster 130 to detect RF outputs of the optical pickup 110 corresponding to each bias voltage, and to output the RF outputs corresponding to the bias voltages. The control unit 160 is configured to compare the magnitudes of each other to determine the bias voltage corresponding to the largest RF signal as the final focus bias voltage, and to provide the determined focus bias voltage to the focus bias adjustment unit 130. It is done.

Description

Focus bias adjuster of DVD system.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video disc recorder (DVDR) system capable of recording, erasing, and reproducing, and more particularly, to a focus bias adjusting apparatus for adjusting a focus bias for optical pickup before recording.

In general, optical discs are CD-only CDs, CD-ROMs, video discs, etc., which can be read only by the user. Information can be recorded once, and the recorded information can be read several times, but cannot be erased or rewritten. It can be divided into a recording type and an erased rewrite type that can repeatedly record, erase, and reproduce information.

Play-only type CD is already replacing the existing LP record board in the sound industry, CD-ROM which is a medium that can be searched when necessary by recording a large amount of information that needs to be widely spread such as encyclopedia, and recently in Korea Video discs and the like, which are rapidly expanding, have already been put into practical use and are in the dissemination stage. Additional recordable optical discs can be used for hospitals and large documents that need to store information such as X-rays, NMR-CTs, ultrasound tomography, and patient care cards. It is used for necessary public offices and mineral veins such as mines and oil fields.

The erasing rewritable optical disc has a magneto-optical type and a phase change type. The phase change type records using crystalline / amorphous reversible changes in the process of heating and cooling the micro part of the medium using a laser, and the information is reflected by the difference in reflectance between the two phases. I am using a method to read it.

1 and 2 show a diagram for explaining a recording, erasing, and reproducing method for such an erased rewritable optical disc.

First, recording is performed when the magnetic thin film oriented in one direction perpendicular to the thin film surface as shown in FIG. 1A is momentarily heated to near the Curie temperature by the laser focused light pulse as shown in FIG. The coercive force of the part is reduced. At this time, only the laser irradiation part heated by the weak magnetic field applied in the direction opposite to the medium magnetization direction is reversed. When the laser pulse is turned off and cooled to room temperature, only this part remains as a stable inverse magnetic field bit and information is recorded.

The erasing is performed by heating the portion where information is recorded as shown in FIG. 1B by means of a laser beam as shown in FIG. By doing so.

On the other hand, reading of the recorded information is performed by using a laser light and a polarizer which are weaker than at the time of recording as shown in FIG. 2C. When the linearly polarized light is reflected from the surface of the perpendicularly magnetized material, the polarization direction depends on the magnetization direction of the material. The magneto-optical Kerr effect which rotates left and right with respect to the polarization direction of this incident light is used (refer FIG. 1 (C)). That is, the polarization direction of the reflected light is rotated counterclockwise when the magnetization direction of the material is downward, and clockwise when it is upward, so that the reflected light passes through the two reflected beams with the analyzer set in advance in a direction that hardly passes the reflected polarization in the unrecorded portion. Then, the reflected light of the unrecorded part has a weak light quantity, and the reflected light of the recorded part passes through the analyzer and is converted into a strong signal of light, which is read by the digital signals '0' and '1' using a photodetector. Done.

As described above, a system for recording, erasing, and reproducing the erase rewritable optical disc is commonly referred to as a DVDR system.

On the other hand, when recording certain data on such an erasing rewritable optical disc, if the focus bias is not properly adjusted, a problem occurs in data reproduction. In other words, when recording certain data on an erasing rewritable optical disk, laser light is emitted as shown in FIG. 2A. If the focus bias is not properly adjusted, the laser power is not properly transmitted to the recording surface of the optical disk. It will not be recorded. Therefore, a problem arises naturally when playing back data that is not recorded properly.

Accordingly, an object of the present invention is to provide a focus bias adjustment apparatus capable of performing recording after accurately adjusting the focus bias in a DVDR system.

A DVDR system for driving an optical disc capable of recording, erasing, and reproducing in order to achieve the above object, comprising: an optical pickup unit for reading and outputting an RF signal from the optical disc; An A / D converter 120 for converting the RF signal read by the optical pickup unit into a digital signal and outputting the digital signal; A focus bias adjuster 130 for adjusting a focus bias voltage of the optical pickup 110; A focus error signal generator 140 generating a focus error signal corresponding to the focus error of the optical pickup 110; A focus servo unit 150 for adjusting the focus of the optical pickup unit 110 by using the focus error signal generated by the focus error signal generator 140 and the focus bias voltage; Sequentially providing a plurality of preset bias voltages to the focus bias adjuster 130 to detect RF outputs of the optical pickup 110 corresponding to each bias voltage, and to output the RF outputs corresponding to the bias voltages. The control unit 160 is configured to compare the magnitudes of each other to determine the bias voltage corresponding to the largest RF signal as the final focus bias voltage, and to provide the determined focus bias voltage to the focus bias adjustment unit 130. It is done.

1 and 2 are diagrams for explaining a recording, erasing, and reproducing method of an erased rewritable optical disc.

3 illustrates a focus bias adjustment apparatus according to a preferred embodiment of the present invention.

<Description of the code | symbol about the principal part of drawing>

100: optical disk 110: optical pickup

120: A / D conversion unit 130: focus bias adjustment unit

140: focus error signal generator 150: focus servo unit

160: control unit

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

3 shows a focus bias adjustment apparatus according to a preferred embodiment of the present invention.

In FIG. 3, the apparatus for adjusting the bias bias converts the RF signal read by the optical pickup unit 110 and the optical pickup unit 110 to read and output a radio frequency (RF) signal from the disk 100 and outputs the digital signal. A / D (Analoge / Digital) converter 120, a focus bias corresponding to the focus bias voltage of the optical biasing unit 130 and the focus bias adjusting unit 130 for adjusting the optical pickup 110, the focus error corresponding to When the focus error signal generator 140 and the focus error signal generated by the focus error signal generator 140 are provided, the signal surface of the optical disc 100 is focused on the laser beam of the optical pickup unit 110. The RF outputs of the optical pickup unit 110 corresponding to each bias value are sequentially provided by providing a plurality of preset bias values to the focus servo unit 150 and the focus bias adjusting unit 130 which perform the focus servo to be located within the depth. Detecting, each The control unit 160 compares the magnitudes of the RF outputs corresponding to the bias values with each other to determine the bias value corresponding to the largest RF signal as the final focus bias value, and then provides the determined focus bias value to the focus bias adjustment unit 130. do.

The operation of the focus bias adjustment device configured as described above is as follows.

First, in order for the optical pickup unit 110 to properly read data from the optical disk 100, the optical plane 100 must be adjusted so that the signal surface of the optical disk 100 is located within the depth of focus of the laser beam of the optical pickup unit 110. Therefore, adjusting the signal plane of the optical disc 100 to be located within a predetermined depth of focus of the laser beam of the optical pickup unit 110 is called focus bias adjustment, and the signal plane of the optical disc 100 is the laser of the optical pickup unit 110. Adjusting the focus to correspond to the minute variation of the optical disc 100 while being located within a certain depth of focus of the beam is commonly referred to as a focus servo.

That is, when a predetermined bias voltage is provided to the focus servo unit 150, the focus servo unit 150 may correspond to the magnitude of the bias voltage and the objective lens (not shown) and the optical disc 100 of the optical pickup unit 110. The objective lens is driven up and down so that the interval is set.

As such, when the optical disk 100 is rotated in a state in which a predetermined interval is set between the objective lens of the optical pickup unit 110 and the optical disk 100, the optical disk 110 vibrates in the up and down directions. A focus error occurs between the objective lens (not shown) of the unit 110 and the disk 100. Therefore, the focus error signal generator 140 generates a signal corresponding to the focus error of the optical pickup unit 110 and provides the signal to the focus servo unit 150. The focus servo unit 150 controls the optical pickup unit 110 to move the objective lens of the optical pickup unit 110 to correspond to the surface vibration of the disk 110 when the focus error signal is provided.

In the system operating as described above, when the recording is performed in a state where the focus bias adjustment for setting the distance between the objective lens of the optical pickup unit 110 and the optical disk 100 is not properly performed, the recording may not be performed properly.

Accordingly, the present invention is intended to ensure that such focus bias adjustment is made accurately.

First, while the optical pickup unit 110 is driven, the controller 160 provides the first bias voltage to the focus bias adjuster 130. The focus bias adjuster 130 provides the first bias voltage to the focus error signal generator 140. The focus error signal generator 140 may add the focus error signal and the first bias voltage according to the driving of the optical pickup unit 110 and provide the first error voltage to the focus servo unit 150.

The focus servo unit 150 sets a predetermined distance between the objective lens of the optical pickup unit 110 and the optical disc 100 to correspond to the magnitude of the first bias voltage, and according to the surface vibration of the optical disc in response to the focus error signal. The optical pickup unit 110 is controlled so that the set interval between the objective lens and the optical disc 100 is changed.

The optical pickup unit 110 reads an RF signal from the optical disc 100 at an interval corresponding to the magnitude of the first bias voltage under the control of the focus servo unit 150, and provides the RF signal to the A / D converter 120. The A / D conversion unit 120 converts the RF signal of the optical pickup unit 110 to digital and provides it to the control unit 160, and the control unit 160 is digitally converted by the A / D conversion unit 120. After detecting the RF signal for a predetermined time, the average value of the magnitude of the detected RF signal during the predetermined time is calculated and stored in the internal memory.

Then, the controller 160 provides the preset second bias voltage to the focus bias adjuster 130. The focus bias adjuster 130 provides the second bias voltage to the focus error signal generator 140. The focus error signal generator 140 may add the focus error signal and the second bias voltage according to the driving of the optical pickup unit 110 and provide the same to the focus servo unit 150.

The focus servo unit 150 sets a predetermined distance between the objective lens of the optical pickup unit 110 and the optical disc 100 to correspond to the magnitude of the second bias voltage, and according to the surface vibration of the optical disc to correspond to the focus error signal. The optical pickup unit 110 is controlled so that the set interval between the objective lens and the optical disc 100 is changed.

The optical pickup unit 110 reads an RF signal from the optical disc 100 at an interval corresponding to the magnitude of the second bias voltage under the control of the focus servo unit 150 and provides the RF signal to the A / D converter 120. The A / D conversion unit 120 converts the RF signal of the optical pickup unit 110 to digital and provides it to the control unit 160, and the control unit 160 is digitally converted by the A / D conversion unit 120. After detecting the RF signal for a predetermined time, the average value of the magnitude of the detected RF signal during the predetermined time is calculated and stored in the internal memory.

As such, the controller 160 sequentially provides a plurality of bias voltages preset by the focus bias adjuster 130 to the focus bias adjuster 130, and then presets RF signals read out corresponding to the magnitude of the bias voltage. The detection is performed for a time period, and the average value of the magnitudes of the respective RF signals detected for a predetermined time period is calculated and stored in the internal memory.

In this case, a large average value of the RF signals indicates that the focus bias adjustment is performed as well.

Accordingly, the controller 160 compares the average values of the respective sizes of the RF signals stored in the internal memory with each other and detects the largest average value. Then, the bias value corresponding to the value having the largest average value for the magnitude of the RF signal is set as the final focus bias value.

As described above, according to the present invention, after detecting the RF signals at predetermined times corresponding to a plurality of bias values, the present invention calculates an average value of the respective RF signals detected during the predetermined time and corresponds to the largest value. By determining the bias value as the final focus bias voltage, it is possible to prevent errors in recording, erasing, and reproducing of the optical disc.

Claims (2)

In a DVDR system driving an optical disc capable of recording, erasing and playing: An optical pickup unit 110 for reading and outputting an RF signal from the optical disk; An A / D converter 120 for converting the RF signal read by the optical pickup unit into a digital signal and outputting the digital signal; A focus bias adjuster 130 for adjusting a focus bias voltage of the optical pickup 110; A focus error signal generator 140 generating a focus error signal corresponding to the focus error of the optical pickup 110; A focus servo unit 150 for adjusting the focus of the optical pickup unit 110 by using the focus error signal generated by the focus error signal generator 140 and the focus bias voltage; Sequentially providing a plurality of preset bias voltages to the focus bias adjuster 130 to detect RF outputs of the optical pickup 110 corresponding to each bias voltage, and to output the RF outputs corresponding to the bias voltages. Of the DVDR system including the control unit 160 which compares the sizes of the two to each other and determines the bias voltage corresponding to the largest RF signal as the final focus bias voltage and then provides the determined focus bias voltage to the focus bias adjustment unit 130. Focus bias adjuster The method of claim 1, wherein the control unit 160 detects the RF signals read out corresponding to the magnitudes of the plurality of bias voltages for a predetermined time, and the magnitudes of the respective RF signals detected for the predetermined time. And calculating a bias voltage corresponding to an RF signal having the largest average among the calculated averages as a final focus bias voltage after calculating an average value for each.