JP2003196830A - Optical pickup and optical disk recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preamplifier which is not to be saturated by servo signals caused by reflected light beams that are reflected from an optical disk during recording. <P>SOLUTION: Reflected light beams from the optical disk are received by a photodetector 21. A photoelectric converted output current of the photodetector 21 is supplied to one of the input terminals of an operational amplifier 22. A switch 23 is provided between a current bias circuit 30 and the input terminal of the operational amplifier 22. Writing gate signals are varied during an information recording and an information reproducing. The switch 23 is controlled so that a bias current is supplied to the input terminal during recording, and during reproducing the bias current is turned off. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup and an optical disc recording / reproducing apparatus for irradiating a recordable optical disc with a light beam to record a signal and for reading a signal recorded on the optical disc. Regarding

[0002]

2. Description of the Related Art As a document disclosing a known technique in the technical field to which the present invention belongs, there is JP-A-2000-182241 (publication date: June 30, 2000).

This publication describes a recordable disc, a DVD-RAM (Digital Versatile).
Disc Random Access Memor
y) An optical disk device for recording a signal on a standard disk and a head amplifier used for this are disclosed.

[0004]

Conventionally, when recording a signal on an optical disc, it was necessary to emit light with a laser element of an optical pickup with full power in order to obtain as much light as possible.

However, since the reflected light of the optical disc is used as a servo signal for controlling the position of the light beam on the optical disc during this recording, the dynamic range of the reproduction signal based on this reflected light becomes excessive. The phenomenon that it becomes large occurs.

Therefore, when amplifying this signal, unless an amplifier with a large dynamic range is used, the amplifier is saturated and the servo information superimposed on the reproduced signal is lost, and as a result, servo processing for the light beam is performed. There is a problem that you can not do.

Therefore, the present invention provides an optical pickup, an optical disc recording / reproducing apparatus, and an amplifier for an optical pickup, which is provided with an amplifier that is not saturated by a reproduction signal due to reflected light reflected from an optical disc during recording. The purpose is to

[0008]

In order to solve the above-mentioned problems, a laser output portion for irradiating an optical disk with a laser beam and a light detection for guiding a reflected light from the optical disk which reflects the laser beam. A photoelectric conversion output current of the photodetector is supplied to an input terminal, an amplifier for obtaining a voltage conversion output, a current bias circuit for outputting a bias current,
By using a switch circuit provided between the current bias circuit and the input terminal of the amplifier, and a signal that changes during recording of the information and during reproduction of the information, the bias current is input during the recording. A circuit for controlling the switch circuit so as to turn off the bias current during reproduction.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, the overall structure of an optical disc recording / reproducing apparatus to which the present invention is applied will be described with reference to FIG.

In the optical disc recording / reproducing apparatus, 100 is an optical disc. 1 is a pickup. The pickup 1 has a laser output section having a laser element and an optical system having an optical path for irradiating the optical disc 100 with a light beam from the laser output section.
The optical system also has an optical path that guides the reflected light reflected from the optical disc 100 to a photodetector (described later).

The information recorded on the optical disc 100 is read by irradiating the light beam from the pickup 1 and reading the reflected light. Information recording on the optical disc 100 is performed by irradiating a light beam from the pickup 1.

At the time of reproducing information, the photoelectric conversion output output from the pickup 1 is the RF (high frequency) amplifier 2, the data slice circuit 3, and the NRZI (Non-Ret).
urn-to-Zero-Inverted) demodulation circuit 4, demodulation circuit 5, ECC (Error-Check-C)
(ode) processing circuit 6 is processed.

At the time of recording information, the recording data includes the modulation circuit 21 and the laser diode (LD) drive circuit 2.
There are two routes. The output of the LD drive circuit 22 controls the laser diode in the pickup 1, whereby laser light is emitted according to the recorded information, and information is recorded on the track of the optical disc 100.

The optical disc 14 is placed on a turntable (not shown) attached to the spindle motor 12. The optical disc 14 is rotated by the rotation of the turntable. This rotation controls the spindle motor 12 circuit. The spindle motor servo circuit 1
Controlled by 3.

As described above, the optical pickup 1 records a signal by irradiating the recording track provided on the signal recording surface of the rotated optical disc 100 with a light beam by causing the laser element 15 to emit light. Alternatively, playback is performed.

Strictly speaking, reproduction is performed by receiving the reflected light of the light beam irradiated on the recording track by the photodetector 21 provided in the optical pickup to obtain a reproduction signal.

When recording and reproducing a signal on the optical disc 100, the position of the light beam on the signal recording surface of the optical disc 100 and the track is in a just focus state and the track is irradiated. The objective lens (not shown) is moved so as to be in the on-track state.

Tracking servo and
It is called Focusing Servo. The tracking servo circuit 10 and the focusing servo circuit 11 move and control an objective lens (not shown) provided in the optical pickup, and in the focus servo, the focus of the light beam is on the signal recording surface, and in the tracking servo, The irradiation position of the light beam is made to follow the recording track.

The tracking servo circuit 10 and the focusing servo circuit 11 receive the reproduction signal reproduced by the RF amplifier 2 to generate a tracking servo signal and a focusing servo signal, respectively, and feedback control the irradiation position of the light beam. .

The RF amplifier 2 amplifies the reproduction signal and transfers it to the data slice circuit 3 for generating digital data in addition to inputting it to the tracking servo circuit 10 and the focusing servo circuit 11.

The data slicing circuit 3 slices the waveform of the reproduced signal at a predetermined timing to form a square wave (digital).
A signal is generated and further input to the NRZI demodulation circuit 4 in the subsequent stage. The NRZI demodulation circuit 4 demodulates the NRZI-modulated square wave as a digital signal and transfers it to the demodulation circuit 5 in the subsequent stage.

The demodulation circuit 6 detects data from the digital signal in units of a predetermined data record length, converts the data into a table,
The demodulated data is obtained and transferred to the ECC processing circuit 5.

The ECC processing circuit 5 receiving the demodulated data,
The digital signal is error-corrected in units of ECC blocks and output as reproduced data.

The address detection circuit 7 detects an address indicating the recording position on the optical disc of the digital data being reproduced, and transfers information based on this address to the track jump circuit 8 in the subsequent stage.

The optical pickup 1 is moved in the radial direction of the optical disc 100 by the torque (rotational force) generated by the pickup motor 9. The pickup motor 9 generates torque under the control of the track jump circuit 8 to control the movement of the optical pickup 1.

For example, when the optical pickup 1 is guided to a predetermined position on the signal recording surface of the optical disk 14 by a command from the microprocessor 14, the address at this predetermined position and the current reproduction detected by the address detection circuit 7 are reproduced. The track jump circuit 8 outputs a track jump signal corresponding to the difference from the address of the position. As a result, the pickup motor 9 generates torque to move the optical pickup 1 to a predetermined position. This operation is called a track jump operation.

Further, what is important in recording / reproducing an optical disc is controlling the number of revolutions of the disc. The spindle motor servo circuit 13 performs this control. The spindle motor servo circuit 13 is the microprocessor 1
In response to the command from 4, the spindle motor servo signal is generated. As a result, the spindle motor 12 is rotated at a predetermined stable rotation speed.

At that time, the spindle motor servo circuit 1
3 monitors the number of revolutions of the spindle motor based on the counter electromotive force generated according to the number of revolutions of the spindle motor 12, and compares the present number of revolutions of the spindle motor 12 with a predetermined number of revolutions set in advance. Detect the difference. A spindle servo signal is generated according to the detection result to maintain the rotation speed of the spindle motor 12 at a predetermined rotation speed. This is called spindle servo processing.

Next, the operation of writing a signal to the optical disc 14 will be described.

Recording data (assuming that the data is an ECC block to which an error correction code has already been added) is
It is input to the modulation circuit 21 and converted into a predetermined bit length. For example, 8 bits are converted to 16 bits. A frame synchronization code or the like is added to this modulated data, and the LD
It is input to the drive circuit 22. LD drive circuit 22
Generates a recording pulse according to the data and drives the laser diode in the pickup 1. Further, in the optical disc, a header area for dividing the physical sector is formed in advance along the recording track, and the header area and the data writable area are alternately set. The address information recorded here is also read during the recording operation. This address information is detected by the address detection circuit 7 via the data slice circuit 3. The address detection circuit 7 detects address information,
In the data area where data is to be recorded, the modulation circuit 2
2. Give a write control signal to the LD drive circuit 22.

FIG. 2 is a circuit block diagram of the preamplifier according to the present invention.

In the figure, numeral 21 is built in the optical pickup 1, and the light beam emitted by the laser element in the optical pickup 1 receives the reflected light reflected on the signal recording surface of the optical disc 100 and reproduces it. It is a photodetector for generating a signal.

The photodetector 21 is composed of a photodiode, and when the reflected light is received, the current i flows according to the intensity of the received reflected light. The photodetector 21 has one end installed and the other end connected to the- (minus) terminal of the operational amplifier 22.

+ (Plus) of the operational amplifier 22
The reference voltage Vref is applied to the terminal, and between the-(minus) terminal of the operational amplifier 22 and the ground,
The photodetector 21 is connected. Further, the- (minus) terminal of the operation amplifier 22 and the output terminal are connected via the resistor 25, and the dynamic range of the reproduction signal Vout is set by the resistance value of the resistor 25.

Further, the- (minus) terminal of the operational amplifier 22 is connected to the current bias source 30 via the switch 23. The switch 23 is ON / OFF controlled by the write gate signal from the modulation circuit 21 described above, for example.

That is, the switch 23 is turned on during the period when the recording pulse is supplied to the laser element (the period during which the data is recorded in the data area), and the period for reading the address information and the complete reproduction mode are set. When turned off. The purpose of this control will be further clarified in the following description.

First, the basic operation is as follows. When a current flows through the photodetector 21, a potential corresponding to the product of the resistance value of the resistor 25 and the current value is generated. This potential and
The difference between the reference voltages occurs as the reproduction signal Vout.

Here, when the switch 23 of FIG. 2 is off, the reference for the input of the operational amplifier 22 is
It becomes the reference potential Vref. On the other hand, the switch 23
Is turned on, the reference for the input of the operational amplifier 22 becomes Vref-R × i (bias). R
Is the resistance value of the resistor 25, and i (bias) is the bias current value supplied from the current bias source 30.

That is, by switching the switch 23, the dynamic range of the operational amplifier 22 changes.

FIG. 3 shows the operation amplifier 24 described above.
Waveform W1 of the reproduction signal obtained during reproduction, waveform W2 obtained when the reflected light during recording is detected, and its reference voltage Vr.
The relationship between ef and Vref−R × i (bias) is shown.

The reference voltage is switched in this manner because the operation amplifier 22 is S / N during reproduction.
This is because the reference voltage Vref and the resistance value of the resistor 25 are set so that the reproduction output can be obtained in the optimum characteristic region of the amplification factor of the operation amplifier 22.

On the other hand, during recording, the laser element is driven with high power. That is, the optical disc 14
When a signal is recorded in, the mark must be surely generated on the signal recording surface, so that the laser element of the optical pickup 1 emits light in the maximum full power state. Therefore, the intensity of the light beam applied to the signal recording surface at this time is also the maximum intensity that the optical pickup 1 can output.

As described with reference to FIG. 1, the light beam of the optical pickup is in a just focus state on the signal recording surface of the optical disc, and is in the on-track state where it is irradiated onto the recording track. So each,
Focus servo processing and tracking servo processing are performed. This controls the system to ensure that the light beam traces the recording tracks on the optical disc.

This servo control is performed also when a signal is recorded on the signal recording surface of the optical disc, and the servo control is performed based on the servo information signal superimposed on the reproduction signal obtained from the photodetector 21 shown in FIG. Is to be applied.

However, the intensity of the light beam applied to the signal recording surface at this time is the maximum intensity that the optical pickup 1 can output, and the level of the reproduction signal based on the reflected light becomes considerably large.

If the level of the reproduction signal becomes too high, the preamplifier will be saturated, and the servo information for realizing the servo control of the light beam will be lost from this reproduction signal.

Therefore, in the apparatus of the present invention, the switch 23 shown in FIG. 2 is controlled to switch the reference potential of the operational amplifier 22 between the reproduction and the recording as shown in FIG. As the control signal for the switch 23, as shown in FIG. 1, a switching signal for turning on / off the modulation output and turning on / off the laser element is used. The switching signal may also use a timing signal output from the microprocessor 14.

As a result, at the time of recording, the dynamic range of the operation amplifier 22 is expanded, the saturation of the preamplifier is suppressed, and the servo information for realizing the servo control of the light beam disappears from the reproduced signal. Prevent it.

The present invention is not limited to the above embodiment. On the output side of the operational amplifier 22,
Further, a dummy amplifier 33 for stabilizing the reference potential may be connected. By connecting the dummy amplifier 33, the reference level of the reproduction signal supplied to the signal processing circuit in the subsequent stage is further stabilized, and is not affected by the switching of the switch 23 described above.

FIG. 4 shows a pulse waveform of the amount of reflected light when recording a signal on an optical disc. The amount of reflected light during recording is comparable to the recording pulse level. This reflected light is detected by the detector 21. At this time, if the reference potential of the operational amplifier 22 is made the same as that at the time of reproducing, the reproduced signal will be distorted. However, in the present invention, since the reference potential is switched and the dynamic range is expanded, the level of the reproduction signal is controlled to be small.

That is, at the time of recording, the dynamic range is sufficiently secured so that the output of the preamplifier is not saturated. As a result, the servo information superimposed on the reproduction signal also remains without being lost. Therefore, the servo information can be surely extracted from the reproduction signal, the tracking servo processing or the focusing servo processing of the light beam can be performed, and the reliability of the device is improved.

As described above, according to the present invention, it is possible to perform the servo processing of the light beam when the signal recording is performed on the optical disk without saturating the operation amplifier and losing the servo information. Become.

[0054]

As described above, according to the present invention, an optical pickup and an optical disc recording / reproducing apparatus having a preamplifier which is not saturated by a servo signal due to reflected light reflected from an optical disc during recording are provided. Can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical disc recording / reproducing device.

FIG. 2 is a circuit block diagram of a preamplifier according to the present invention.

FIG. 3 is a diagram showing an example of an output signal waveform of a preamplifier.

FIG. 4 is a diagram showing a level of a recording signal when recording a signal on an optical disc and a level of a reproduction signal in comparison.

[Explanation of symbols]

15 ... Laser element, 21 ... Photodetector, 22 ... Operation amplifier, 23 ... Switch, 25 ... Resistor.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5D090 AA01 BB04 CC01 CC04 CC16                       DD03 EE11 FF41 HH01 KK03                 5D119 AA09 AA21 BA01 BB03 DA01                       DA05 KA43                 5D789 AA09 AA21 BA01 BB03 DA01                       DA05 KA43

Claims (3)

[Claims] 1. A laser output unit for irradiating an optical disc with laser light, a photodetector to which reflected light from the optical disc reflecting the laser light is guided, and a photoelectric conversion output current of the photodetector. Is supplied to an input terminal to obtain a voltage conversion output, a current bias circuit that outputs a bias current, a switch circuit provided between the current bias circuit and the input terminal of the amplifier, and the recording of the information. A circuit for controlling the switch circuit so as to supply the bias current to the input terminal during recording and to turn off the bias current during reproduction by using a signal that changes between time and reproduction of the information. An optical pickup characterized by being provided. 2. The optical pickup according to claim 1, wherein the signal that changes between when the information is recorded and when the information is reproduced is introduced from a modulation circuit that modulates the recorded data. 3. A laser output unit for irradiating an optical disc with laser light, a photodetector to which reflected light from the optical disc reflecting the laser light is guided, and a photoelectric conversion output current of the photodetector. Is supplied to an input terminal to obtain a voltage conversion output, a current bias circuit that outputs a bias current, a switch circuit provided between the current bias circuit and the input terminal of the amplifier, and the recording of the information. A circuit that outputs a signal that changes between the time and the time of reproducing the information, supplies the bias current to the input terminal during recording, and controls the switch circuit so that the bias current is turned off during reproduction. An optical disc recording / reproducing device characterized by being provided.