KR100235787B1 - Apparatus for controlling focus offset value in a digital video disk recorder - Google Patents

Abstract

The present invention relates to an apparatus for adjusting focus offset of a digital video disc recorder. The laser beam output from the laser diode 14 is picked up and transmitted to the disc when the recording function is executed, and the light reflected from the disc D is picked up. An optical pickup unit 10 for outputting; A light amount detector 20 which detects a light amount of reflected light output from the optical pickup unit 10; A focus error detector 30 which detects a focus error signal based on an output signal of the light quantity detector 20; A first comparator 60 for comparing the light quantity signal detected by the light quantity detector 20 with a preset reference level Vref and outputting the comparison signal; A first buffer 70 buffering the comparison signal provided from the first comparator 60; An amplifier unit 80 for amplifying and outputting the output light of the laser diode 14 to a predetermined gain; A second comparison unit 90 for comparing the output signal of the amplifier unit 80 with a preset reference laser signal level Vl and outputting the comparison signal; A second buffer 100 for buffering the output signal of the second comparator; A microcomputer (110) generating a control signal for adjusting a focus offset according to output signals of the first buffer and the second buffer (70, 90); A focus offset adjuster 40 which sets the focus offset according to a control signal provided from the microcomputer 110 and outputs a compensation signal for compensating a focus error according to the set focus offset; And a pickup driver 50 for driving the optical pickup unit 10 according to the compensation signal provided from the focus offset adjuster 40.

Description

Focus Offset Adjuster of Digital Video Disc Recorder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video disc recorder. In particular, when the recording function is executed, the focus offset is set incorrectly, so that the amount of laser light reaching the disc is smaller than the desired amount, thereby preventing data from being recorded smoothly. A focus offset adjusting device of a digital video disc recorder which adjusts a focus offset so that it can be done.

With the development of audio and video media, optical disc players for recording and reproducing video and audio data on semi-permanent optical discs have been developed.

Such an optical disc player reproduces an image and / or audio recorded on an optical disc and outputs it through a screen and / or a speaker, and has a higher signal-to-noise ratio than conventional image and / or audio reproducing apparatus, resulting in better image quality and / or Or it can reproduce the signal with sound quality, it does not generate noise due to irregular reproduction and modulation, very low distortion, no ghost and random access, so it is rapidly developed and widely distributed. There is a trend.

In addition, the optical disc used for the playback and recording functions in the optical disc player is a play-only type in which the user can only play information, such as a CD, CD-ROM, and video disc, depending on its function and use. The recorded information can be divided into an additional recording type that can be read many times but not erased and rewritten, and an erased rewrite type that can repeatedly record, erase and reproduce the 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 is recorded using a crystalline / amorphous reversible change in the process of heating and cooling the micro part of the medium using a laser. I am using a method to read it.

In general, recording of a magneto-optical optical disk causes the coercive force of the heated micro part to be reduced when the magnetic thin film unidirectionally oriented to the thin film surface is momentarily heated to near the Curie temperature by a laser focused light pulse. 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 domain bit and information is recorded.

The erasing is performed by heating the portion where the information is recorded by the laser beam, and then applying the direction of the external magnetic field at the time of cooling as opposed to at the time of recording to have the original magnetization direction.

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. When the linearly polarized light is reflected from the surface of the vertically magnetized material, the polarization direction is left with respect to the polarization direction of the incident light when the linearly polarized light is reflected from the surface of the perpendicular magnetized material Use the magneto-optical Kerr effect which rotates to the right and the right, respectively. 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 converted into a digital signal '0' and '1' by using a light detecting element. Will be read.

As described above, a system for recording, erasing, and reproducing the erase rewritable optical disc is commonly referred to as a digital video disk recorder (DVDR).

On the other hand, in a recordable optical disc, a pregroove is formed in a spiral shape in advance, and a land portion is formed between the pregroove and the pregroove, and data can be recorded in the pregroove and the land portion. In the pregroove or land portion, a sync code or absolute address is pre-recorded in the form of a wobble or pit. A recordable area except for an area where the sync code or absolute address is pre-recorded is called a program area. do.

On the other hand, in order to record data on the recordable optical disc described above in the DVDR, the disc is rotated at a constant linear velocity by using the sync code and the absolute address reproduced by reproducing the pre-recorded area, that is, the area where the sync code and the absolute address are recorded. Normalized data should be recorded while controlling the speed and confirming the recording position.

In addition, in recording data on an optical disc in a DVDR, the power of the laser, the recording medium, that is, the optical disc and the focus offset are very important factors. In particular, even if the laser power and the recording medium are normal among these factors, when the focus offset is set incorrectly, the amount of laser power reaching the medium is smaller than the desired amount, so that the amount of reflection on the recording medium, i. There was a problem that the number of data may not be recorded smoothly.

1A, 1B and 1C are diagrams showing the output power of a laser, a pit formed on a disk surface, and a radio frequency (RF) signal reflected on the disk surface during recording.

As shown in Fig. 1, the pits recorded on the disc are recorded on the disc at a predetermined time (A, B) after laser output due to the heat transfer delay of the laser, i.e. the light on the disc. The RF signal reflected on the disk during recording is reflected and output at about the same time as the output of the laser power because the transmission speed of light is much faster than the thermal delay speed. That is, the laser output point, the point at which pits are formed on the disc, and the point of time of the reflected RF signal do not coincide with each other due to the heat transfer delay on the disc.

Therefore, taking into account the delay time of data recording due to the heat transfer delay, the amount of light reflected on the disc, specifically the pit recorded on the disc, after a predetermined time after outputting the laser, i.e., the heat transfer delay time, becomes constant. Only when the focus offset is set can data be properly recorded on the disk.

Accordingly, the present invention has been made to solve the above-mentioned problem, and an object of the present invention is to set a digital data offset by setting a focus offset in consideration of a heat transfer delay when a recording function is executed in a digital video disc recorder. It is to provide a focus offset adjusting device of a disc recorder.

According to a preferred embodiment of the present invention for achieving this purpose, a focus offset is set so that data can be written smoothly in consideration of the heat transfer delay on the disk of the laser output from the laser diode when the recording function is executed. A focus offset adjustment apparatus of a digital video disc recorder for setting, comprising: an optical pickup unit which picks up and transmits laser light output from the laser diode to the disc when the recording function is executed, and picks up and outputs light reflected from the disc A light amount detector for detecting a light amount of reflected light output from the optical pickup unit, a focus error detector for detecting a focus error signal based on an output signal of the light amount detector, and a light amount signal detected at the light amount detector; Compare with the set reference level A first comparator for outputting a call, a first buffer for buffering a comparison signal provided from the first comparator, and amplifying and outputting the output light of the laser diode with a predetermined gain when a write function is executed; An amplifier unit, a second comparison unit comparing the output signal of the amplifier unit with a preset reference laser signal level and outputting the comparison signal, a first buffer buffering an output signal of the second comparison unit, and the first buffer And a microcomputer generating a control signal for adjusting the focus offset according to the output signal of the second buffer, and setting the focus offset according to the control signal provided from the microcomputer, and adjusting the focus error according to the set focus offset. A focus offset adjuster for outputting a compensated signal for compensating and a compensation signal provided from the focus offset adjuster La is included and configured to pickup driving unit for driving the optical pickup unit.

1A, 1B, and 1C show an output power of a laser, a pit formed on a disk surface, and an RF signal reflected on the disk surface during recording;

2 (a), (b) and (c) are diagrams for explaining setting of a focus offset in the focus offset adjusting apparatus according to the present invention;

Fig. 3 is a block diagram showing a focus offset adjusting device of a digital video disc recorder according to the present invention.

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

10: optical pickup section 12: objective lens

14: laser diode 20: light amount detector

30: focus error detection unit 40: focus offset adjustment unit

50: pickup drive unit 60, 90: comparison unit

70, 100: buffer 110: microcomputer

D: Disk

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

2A, 2B, and 2C are diagrams for explaining setting of a focus offset in a focus offset adjusting apparatus according to the present invention.

That is, the present invention, as shown in Fig. 2 (a), after the laser output (V1) (T1) after the heat transfer delay time (T) has elapsed (T2) is shown in Fig. 2 (b). The data is recorded on the disk as shown, and the RF reflected back after the heat transfer delay time T elapses as shown in Fig. 2C, i. The focus offset value is adjusted so that the output of the signal reaches a preset reference level Vref.

On the other hand, the heat transfer delay time (T) and the reference level (Vref) can be obtained by experimenting the average time and level. In the end, in order for the recording function to be smoothly performed, the recording function is executed and the laser is output to the disk. The focus offset should be set so that the time for which the reflection amount reaches the reference level Vref becomes the heat transfer delay time T obtained by the experiment.

3 is a schematic block diagram of a digital video disc recorder employing a focus offset adjusting device according to the present invention for setting the focus offset as described in FIG.

As shown in FIG. 3, the present invention provides an optical pickup unit 10 including a laser diode (LD) 14 and an objective lens 12, a light amount detector 20, a focus error detector 30, and a focus offset adjuster. It comprises 40, the pickup drive part 5, the 1st and 2nd comparison parts 60 and 90, the 1st and 2nd buffers 70 and 100, the amplifier part 80, and the microcomputer 110. .

In addition, as is generally known, the recording waveform generating section 5 converts data to be recorded, which is input from the outside, into waveform signals for recording on a disk, and the LD driving section 8 writes the recording waveform generating section ( In response to the output signal of 5), the LD 14 is driven to record data on the disk.

On the other hand, according to the present invention, the recording function is executed and data to be recorded from the outside is input to the recording waveform generator 5, and the LD driver 8 is driven by the LD (8) according to the output signal of the recording waveform generator 5; 14, the objective lens 12 picks up the laser light incident from the LD 14 and irradiates it onto the disk D. At the same time, the objective lens 12 picks up the light reflected on the disk D to detect the amount of light. To provide.

On the other hand, when the LD 14 is driven and outputs a laser, the amplifier unit 80 amplifies the size of the laser output from the LD 14 with a predetermined gain, that is, with a gain smaller than 1, and thus the second comparator ( 90, and the comparison unit 90 compares the reference output level Vl based on the preset reference level, that is, the laser output level at the time of data recording, wherein the output signal of the amplifier unit 80 If the level is greater than or equal to the reference level of the comparator 90, a 'high' signal is generated and if it is less, a 'low' signal is generated to the second buffer 100. The amplification gain of the amplifier 80 is less than 1 because the level of the laser power at the time of recording is very high so as to reduce the comparator 90 to a level comparable.

In addition, the second buffer 100 buffers the output signal of the comparator 90 to the microcomputer 110, so that the microcomputer 110 applies the laser of the predetermined level Vl for the LD 14 to write data. Recognize the time of output.

Meanwhile, the light amount detector 20 detects the light amount of the reflected light provided from the optical pickup unit 10 and provides the light amount detector 20 to the focus error detector 30 and the first comparator 60. Then, the focus error detector 30 detects the focus error signal from the light amount signal provided from the light amount detector 20 and provides the focus error signal to the focus offset detector 40.

At the same time, the first comparator 60 compares the output signal of the light quantity detector 20 with the preset reference level Vref, and when the output signal of the light quantity detector 20 is greater than the reference level Vref, 'low'. When the signal is the same or smaller, the 'low' signal is provided to the microcomputer 110 through the first buffer 70 so that the microcomputer 110 can detect a time when the amount of reflected light reaches the reference level Vref. do.

Accordingly, the microcomputer 110 generates a control signal for setting the focus offset according to the output signals of the first buffer 70 and the second buffer 70 to the focus offset adjuster 40. That is, in detail, the microcomputer 110 receives the first time when the 'high' signal is first input from the second comparator 90 through the second buffer 100, that is, as shown in FIG. ) Is the time T2 at which the 'high' signal is first inputted from the first comparator 60 through the first buffer 70 from the time point T1 at which the laser outputs a predetermined level Vl, that is, reflected light. The focus offset adjusting unit 40 is controlled to count the time until the level reaches the preset reference voltage Vref so that the counted time becomes the preset delay time T. As described above, the preset reference voltage Vref is the light quantity level of the reflected light at the initial position at which the pits are formed.

The focus offset adjustment unit 40 adjusts the offset value according to the control signal for offset adjustment provided from the microcomputer 110 as described above, and provides the focus error provided from the focus error detection unit 30 according to the adjusted offset value. The pickup signal is provided to the pickup driver 50 to compensate for the error, and accordingly, the pickup driver 50 drives the optical pickup unit 10 to perform the focus servo so that data recording can be performed smoothly.

Meanwhile, according to the present invention, the first buffer 70 and the second buffer 100 may directly apply an analog signal output from the first comparator 60 and the second comparator 90 to the microcomputer 110. Since it cannot be connected, it is connected between the first and second comparators 60 and 90 and the microcomputer 110 to buffer the output signals of the first and second comparators 60 and 90.

As described above, the present invention smoothly saves data by preventing the amount of laser light reaching the disc from being smaller than necessary for data recording due to an incorrect setting of the focus offset when the recording function is executed in the digital video disc recorder. It has the effect of being able to record.

Claims (4)

Focus offset adjusting device of a digital video disc recorder for setting a focus offset so that data can be recorded smoothly in consideration of the heat transfer delay on the disc of the laser output from the laser diode 14 when the recording function is executed. To An optical pickup unit (10) which picks up and transmits the laser light output from the laser diode (14) to the disc when the recording function is executed, and picks up and outputs the light reflected from the disc (D); A light amount detector 20 for detecting a light amount of reflected light output from the optical pickup unit 10; A focus error detector (30) which detects a focus error signal based on an output signal of the light amount detector (20); A first comparator 60 for comparing the light quantity signal detected by the light quantity detector 20 with a preset reference level Vref and outputting the comparison signal; A first buffer (70) for buffering the comparison signal provided from the first comparison unit (60); An amplifier unit 80 for amplifying and outputting the output light of the laser diode 14 to a predetermined gain when executing a recording function; A second comparison unit (90) for comparing the output signal of the amplifier unit (80) with a preset reference laser signal level (Vl) and outputting the comparison signal; A second buffer (100) for buffering the output signal of the second comparator; A microcomputer (110) generating a control signal for adjusting the focus offset according to output signals of the first and second buffers (70, 90); A focus offset adjuster 40 for setting the focus offset according to the control signal provided from the microcomputer 110 and outputting a compensation signal for compensating the focus error according to the set focus offset; And a pickup driving unit (50) for driving the optical pickup unit (10) in accordance with a compensation signal provided from the focus offset adjusting unit (40). 2. The apparatus of claim 1, wherein the amplification gain of the amplifier unit (80) is less than one. The method of claim 1, wherein the first comparator 60 compares the light quantity signal detected by the light quantity detector 20 with a preset reference level Vref and outputs the comparison signal. When the light quantity signal output from the signal is greater than the preset reference level (Vref) generates a 'low' signal, if the same or less than the 'low' signal, the second comparator 90 of the amplifier unit 80 Compares the output signal with a preset reference level Vl and outputs the comparison signal, and generates a low signal when the light quantity signal output from the amplifier unit 80 is smaller than the preset reference level Vl. A focus offset adjuster of a digital video disc recorder, characterized in that it generates a 'high' signal if greater than or equal to. 4. The microcomputer 110 of claim 3, wherein the microcomputer 110 receives a first signal from the first comparator 60 from the time when the 'high' signal is first input from the second comparator 90 through the second buffer 100. The focus offset adjustment unit 40 is controlled by counting up to a time point at which the 'high' signal is first input through the buffer 70 and reaching the preset heat transfer delay time T. Focus offset adjustment device of a digital video disc recorder, characterized in that the setting.

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