KR19980078985A - Servo Control of Digital Video Disc Recorder - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control apparatus for a digital video disc recorder, wherein the optical pickup unit (30) generates light for data recording on a disc when the recording function is executed, and picks up the light reflected from the disc and detects the amount of light. A focus / tracking error detector 40 which detects a focus and tracking error signal based on the light quantity signal provided from the optical pickup section 30; An analog / digital (A / D) converter 50 for converting the focus and tracking error signals detected by the focus / tracking error detector 40 into digital signals; A control unit 60 for generating a control signal for performing a tracking servo and a focus servo in response to a change in the amount of reflected light when the recording function is executed; A compensation unit 200 which sets a compensation gain according to a control signal provided from the control unit 60 and generates a digital compensation signal for compensating the focus and tracking error signals provided from the A / D converter 50 accordingly. ; A digital / analog (D / A) converter 100 for converting a compensation signal of the compensation unit 200 into an analog signal; And a pickup driving unit 110 for driving the optical pickup unit 30 according to the analog compensation signal provided from the D / A converter 100 to perform the focus servo and the tracking servo, which is generated when the recording function is executed. The focus and tracking servos can be controlled smoothly regardless of the variation in the amount of reflected light.

Description

Servo Control of Digital Video Disc Recorder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control apparatus for a digital video disc recorder, and more particularly, to a servo control of a digital video disc recorder capable of appropriately performing a focus servo and a tracking servo in response to a change in an optical signal reflected from a disk surface when a recording function is executed. Relates to a device.

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

Such an optical disc system reproduces an image and / or an 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 such functions as the playback and recording in the optical disc system is a play-only type in which the user can only play information such as a CD, CD-ROM, and a video disc, depending on the function and purpose of recording. Thereafter, the recorded information can be divided into an additional recording type which can be read many times but cannot be 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).

In the 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, conventional digital video disc recorders generally perform focus and tracking servos with the same gain during disc reproduction and data recording.

Figure 1 shows a gain characteristic curve in the frequency domain of a conventional digital video disc recorder.

As shown in Fig. 1, 'a' and 'd' are gain and phase characteristic curves of a digital video disc recorder at the time of reproduction, and 'b' represents the gain characteristic curves at the time of recording.

That is, as can be seen from 'a' and 'b', the laser power becomes stronger during recording, so the reflected light amount is increased, so the gain characteristic is increased, and as shown through 'f', a gain margin (gain) can be seen. margin is reduced. In addition, when the recording function is actually executed, the gain characteristic curve causes a large change in the disk reflection amount, that is, a large difference in the reflection amount, so that the variation in the gain becomes large as shown in the 'g' of the characteristic curve of 'c'.

Thus, as shown by the 'h' of the 'd' characteristic curve, there is a certain phase margin during playback, but as shown by 'i', the phase margin becomes nearly zero during recording, so the system It becomes unstable. That is, a difference in reflection amount occurs due to the variation of the laser output power, and accordingly, the sensor gain of the servo system fluctuates, thereby decreasing the phase margin and the gain margin, thereby making the servo unstable.

As a result, in order to solve the instability of the system, it is necessary to increase the phase margin, that is, widen the compensation area, so as to have the characteristic 'e' during recording.

Accordingly, the present invention has been conceived in view of the above, and an object of the present invention is to smoothly control recording by controlling the instability of the servo generated by the difference in the amount of reflection of light on the disc when the recording function is executed in the digital video disc recorder. To provide a servo control device for a digital video disc recorder capable of executing focus servo and tracking servo.

According to a preferred embodiment of the present invention for achieving the above object, in the servo control apparatus of the digital video disc player for controlling the instability of the focus and tracking servo according to the difference in the amount of reflected light when the recording function is executed in the digital video disc recorder And an optical pickup unit for generating data for recording data on the disk when the recording function is executed, thereby picking up the light reflected from the disk and detecting the amount of the light, and focusing on the basis of the light amount signal provided from the optical pickup unit. A focus / tracking error detector for detecting a tracking error signal, an analog / digital (A / D) converter for converting the focus and tracking error signals detected by the focus / tracking error detector into a digital signal, and the amount of reflected light when a recording function is executed Tracking Servo and Focus Servo Compensation for generating a control signal for generating a control signal and a compensation gain according to the control signal provided from the controller, and accordingly generates a digital compensation signal for compensating the focus and tracking error signals provided from the A / D converter. And a digital servo (D / A) converter for converting the compensation signal of the compensator into an analog signal, and the optical pickup unit according to the analog compensation signal provided from the D / A converter. It is configured to include a pickup drive to be made.

1 is a diagram showing a gain characteristic curve in the frequency domain of a conventional digital video disc recorder.

2 is a block diagram showing a servo control apparatus of a digital video disc recorder according to a preferred embodiment of the present invention;

3 is a detailed block diagram of a compensator according to the present invention shown in FIG. 2;

4 is a diagram illustrating a gain characteristic curve in a frequency domain of a compensation unit according to the present invention.

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

10: recording waveform generating unit 20: LD control unit

30: optical pickup section 40: focus / tracking error detection section

50: A / D converter 60: control unit

70: low frequency compensation unit 80: phase compensation unit

90: noise reduction part 100: D / A converter

110: pickup drive unit 200: compensation unit

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

2 is a block diagram showing a servo control apparatus of a digital video disc recorder according to a preferred embodiment of the present invention.

As shown in FIG. 2, the present invention includes an optical pickup unit 30, a focus / tracking error detector 40, an A / D converter 50, a controller 60, a compensator 200, and a D / A converter. 100 and the pickup drive unit 110 are configured. Meanwhile, the compensator 200 includes a low frequency compensator 70, a phase compensator 80, and a noise remover 90.

A servo control apparatus for a digital video disc recorder according to a preferred embodiment of the present invention will be described in detail with reference to FIG. 2.

When a recording function for recording predetermined data on a disk is executed, the recording waveform generator 10 generates a recording waveform signal according to the recording data input from the outside and provides the recording waveform signal to the laser diode (LD) controller 20. Then, the LD control unit 20 drives an LD (not shown) which is embedded in the optical pickup unit 30 and outputs laser light for data recording in accordance with the recording waveform signal provided from the recording waveform generating unit 10, Accordingly, the LD outputs laser light of a predetermined level to record data on the disc.

When data recording is performed as described above, at the same time, the optical pickup unit 30 picks up the light output for data recording and reflected on the disk, and detects the light amount of the picked-up light to detect the focus / tracking error detection unit 40. To provide. Then, the focus / tracking error detection unit 40 detects the focus and tracking errors and provides them to the A / D converter 50 in accordance with the light amount signal provided from the optical pickup unit 30. Since the change in the amount of light is greater, the detected focus error signal and tracking error signal will appear larger than the focus and tracking error signal at the time of reproduction.

Meanwhile, the A / D converter 50 converts the focus and tracking error signals provided from the focus / tracking error detector 40 into digital signals and provides them to the compensation unit 200.

On the other hand, when the above-described data recording is executed, the controller 60 provides the compensator 200 with a control signal that allows the tracking servo and the focus servo to be made in response to a change in the amount of reflected light when the recording function is executed. By resetting the compensation gain of the compensation unit 200 to match the recording function.

According to the present invention, the compensator 200 includes a low frequency signal compensator 70 for compensating a low frequency signal region, a phase compensator 80 for compensating a phase error, and a noise agent for removing high frequency noise components. Rejection 90, and the compensation gain is reset to compensate for the focus error and tracking error caused by the variation of the reflected light amount in accordance with the control signal provided from the control unit 60, respectively, the A / D converter 50 The D / A converter 100 provides a compensation signal for compensating a low frequency signal region, compensating for a phase error, and removing a high frequency noise signal in accordance with a focus and tracking error signal provided through a signal.

In addition, the D / A converter 100 converts the digital compensation signal provided from the phase compensator 200 into an analog signal and provides the analog signal to the pickup driver 110. Accordingly, the pickup driver 110 is an optical pickup unit 30. ) So that focus and tracking servos can be made in response to variations in the amount of reflected light during data recording.

3 is a detailed block diagram of the low frequency compensator 70, the phase compensator 80, and the noise remover 90 constituting the phase compensator 200 illustrated in FIG. 2. A gain characteristic curve for explaining gain characteristics in the frequency domain of the compensator 200 illustrated in FIG.

An operation of the compensator 200 according to the present invention will be described with reference to FIGS. 3 and 4.

The low frequency compensator 70 includes two delay units 71 and 74 and an amplifier 72 that determines the pole Klp value of the low frequency compensator 70 according to a gain set by the control of the controller 60. ) And an amplifier 75 for determining a zero (Klz) value of the low frequency compensator 70 according to the gain set by the control of the controller 60, the delay unit 71 and the amplifier 72. And an adder 73 for summing the output value through the delay value 74 and the output value through the amplifier 75. That is, the low frequency compensator 70 sets the gains of the amplifiers 72 and 75 according to the control of the controller 60 so that the pole Klp and zero Klz values change. As shown in FIG. 5, the pole value Klp and the zero value Klz are shifted to the right to widen the low frequency signal compensation region.

The phase compensator 80 determines two delay units 81 and 84 and an amplifying unit for determining a zero Kpz value of the phase compensator 80 according to a gain set by the control of the controller 60. (82), an amplifier (85) for determining the pole (Kpp) value of the phase compensator (80) in accordance with the gain set by the control of the controller (60), the delay unit (81), and the amplifier (82). And an adder 83 for summing output values through the delay value 84 and the output values through the delay unit 84 and the amplifying unit 85. That is, in the phase compensator 80, gains of the amplifiers 82 and 85 are set under the control of the controller 60 so that the pole Kpp value and the zero Kpz value change. As shown in Fig. 4, the pole (Kpp) value and the zero (Kpz) value are shifted to the right to widen the phase compensation region.

In addition, the noise removing unit 90 includes two delay units 91 and 94 and an amplifying unit that determines a zero Kpz value of the noise removing unit 90 according to a gain set by the control of the control unit 60. (92), an amplifier (95) for determining the pole (Kpp) value of the noise canceller (90) in accordance with the gain set by the control of the controller (60), the delay unit (91), and the amplifier (92). And an adder 93 for summing output values through the delay unit 94 and the output values through the delay unit 94 and the amplification unit 95. That is, the noise removing unit 90 resets the gain of the amplifiers 82 and 85 under the control of the control unit 60 so that the pole Khp value and the zero Khz value change. As shown in FIG. 4, the pole (Khp) value and the zero (Khz) value are shifted to the right to widen the noise removing area.

Therefore, according to the present invention, the low frequency compensator 70, the phase compensator 80, and the noise canceller 90 constituting the compensator 200 may have the pole value and zero under the control of the controller 60 during the recording function. As can be seen from Fig. 4, since the gain margin and the phase margin are reset in a direction in which the gain margin increases, that is, the compensation region is widened, the focus and tracking servos are compensated by compensating the focus and tracking errors regardless of the variation in the amount of reflected light. You can run it.

As described above, the present invention has the effect that the digital video disc recorder can smoothly control the focusing and tracking servo regardless of the variation in the amount of reflected light generated when the recording function is executed.

Claims (2)

In the servo control apparatus of the digital video disc player for controlling the instability of the focusing and tracking servo according to the difference in the amount of reflected light when the recording function is executed in the digital video disc recorder, An optical pickup section 30 which generates light for recording data on the disk when the recording function is executed, thereby picking up the light reflected from the disk and detecting the amount of light; A focus / tracking error detector (40) for detecting focus and tracking error signals based on the light quantity signal provided from the optical pickup section (30); An analog / digital (A / D) converter 50 for converting the focus and tracking error signals detected by the focus / tracking error detector 40 into digital signals; A control unit 60 for generating a control signal for performing a tracking servo and a focus servo in response to a change in the amount of reflected light when the recording function is executed; Compensation unit 200 that sets the compensation gain according to the control signal provided from the control unit 60, and generates a digital compensation signal for compensating the focus and tracking error signal provided from the A / D converter 50 accordingly. Wow; A digital / analog (D / A) converter 100 for converting the compensation signal of the compensation unit 200 into an analog signal; Servo control of the digital video disc recorder including a pickup driver 110 driving the optical pickup unit 30 according to an analog compensation signal provided from the D / A converter 100 to perform focus servo and tracking servo. Device. The method of claim 1, wherein the compensation unit 200; A digital signal comprising a low frequency compensator 70 for compensating for a low frequency signal region, a phase compensator 80 for compensating for a phase error, and a noise remover 90 for removing high frequency noise components. Servo control of video disc recorder.