JP2003217161A - Optical head, recording and reproducing apparatus, and method for controlling amplifier circuit for the optical head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical head, a recording and reproducing apparatus, and a control method for an amplifier circuit for the optical head for properly controlling an amplification factor of a detection signal of a reflected light beam corresponding to the increase/decrease in the luminous intensity of a light beam. <P>SOLUTION: Since a Zener diode 28 is nonconductive when a voltage applied to the Zener diode 28 is a breakdown voltage of the Zener diode 28 or below, an amplification factor A1 (first amplification factor) of the amplifier circuit 20 is decided depending on a resistance R1 of a first feedback resistor 24. Since the Zener diode 28 is conductive when a voltage applied to the Zener diode 28 exceeds a breakdown voltage of the Zener diode 28, an amplification factor A2 (second amplification factor) of the amplifier circuit 20 is decided depending on a combined resistance R12 of a resistance value R1 of the first feedback resistor 24 and the resistance value R2 of a second feedback resistor 26. <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 a recording / reproducing apparatus for recording / reproducing various information on / from an optical recording medium, an optical head provided in various optical devices such as this recording / reproducing apparatus, and control of an amplifier circuit in the optical head. Regarding the method.

[0002]

2. Description of the Related Art For example, when reproducing or recording a recording signal on an optical disk such as a CD or a CD-R, the rotational speed of the optical disk is, for example, 4 ×, 8 ×, 16 ×, 2 ×.
There is a recording / reproducing device configured to switch between 4 × speed and 32 × speed. The optical head provided in such a recording / reproducing apparatus is required to increase the light intensity of the light beam with which the optical disc is irradiated as the rotational speed of the optical disc increases, especially during recording. The reason is that sufficient thermal energy is applied to the recording layer of the optical disc during recording. Further, the optical head is provided with a photodetecting means for detecting a reflected light beam from the optical disk and an amplifier circuit for amplifying a detection signal output from the photodetecting means, and based on the amplified detection signal. Thus, a focus error signal, a tracking error signal, and a speed detection signal are generated. Therefore, when the intensity of the light beam is switched, the light intensity of the reflected light beam also changes, and the detection signal also increases or decreases.

[0003]

In such an optical head, when the detection signal exceeds the saturation level of the amplification characteristic of the amplification circuit due to an increase in the light intensity of the light beam emitted from the light source, S of the output signal of the amplifier circuit
Since the N ratio is deteriorated, it is necessary to control the amplification degree of the amplification circuit so that the detection signal does not exceed the saturation level of the amplification characteristic of the amplification circuit. The present invention is
The optical head, the recording / reproducing device, and the optical head are capable of appropriately controlling the amplification degree of the detection signal of the reflected light beam in response to the increase or decrease in the light intensity of the light beam. It is an object of the present invention to provide a method of controlling an amplifier circuit in.

[0004]

In order to achieve the above object, an optical head of the present invention has a light source for emitting a light beam, and a light for converging the light beam emitted from the light source and irradiating the optical recording medium. Condensing means, condensing means for condensing the light beam emitted from the light source and irradiating the light on the optical recording medium, and light beam emitted from the light source to the optical recording medium and from the optical recording medium. A light separating means for separating the reflected light beam,
An optical head comprising: a photodetector that receives the reflected light beam separated by the light separator and outputs a detection signal corresponding to the light intensity of the reflected light beam; and an amplifier circuit that amplifies the detection signal. , Amplification factor control means for controlling the amplification factor of the amplification circuit is provided, and the amplification factor control means controls the amplification factor when the level of the detection signal is equal to or lower than a predetermined threshold value. The amplification factor A1 is 1, and when the level of the detection signal exceeds the threshold value, the second amplification factor A2 is lower than the first amplification factor.
Therefore, according to the optical head of the present invention, when the light intensity of the light beam emitted from the light source is low, the detection signal is amplified with the amplification factor A1, and when the light intensity of the light beam emitted from the light source is high, The detection signal is amplified at an amplification rate A2 lower than the amplification rate A1.

Further, the recording / reproducing apparatus of the present invention irradiates the drive means for holding and rotating the optical recording medium and the optical recording medium which is rotationally driven by the drive means with light so that the optical recording medium is driven. An optical head for detecting reflected light, and a reproduction signal processing circuit for generating a reproduction signal based on a detection signal from the optical head, wherein the optical head includes a light source for emitting a light beam, and a light source for outputting the light beam. Light converging means for converging the emitted light beam and irradiating the optical recording medium, and separating the light beam emitted from the light source to the optical recording medium and the reflected light beam from the optical recording medium. Light separation means,
Recording / reproducing provided with light detection means for receiving the reflected light beam separated by the light separation means and outputting a detection signal corresponding to the light intensity of the reflected light beam, and an amplification circuit for amplifying the detection signal. In the apparatus, an amplification factor control means for controlling the amplification factor of the amplification circuit is provided, and the amplification factor control means controls the amplification factor when the level of the detection signal is below a predetermined threshold value. Is the first amplification factor A1, and when the level of the detection signal exceeds the threshold value, the second amplification factor A2 is lower than the first amplification factor. . Therefore, according to the recording / reproducing apparatus of the present invention, when the light intensity of the light beam emitted from the light source is low, the amplification factor A
The amplification of the detection signal is performed at 1, and when the light intensity of the light beam emitted from the light source is high, the amplification of the detection signal is performed at the amplification rate A2 lower than the amplification rate A1.

Further, a method of controlling an amplifier circuit in an optical head according to the present invention comprises a light source for emitting a light beam, and a light condensing means for condensing the light beam emitted from the light source and irradiating the optical recording medium. A light separating unit for separating a light beam emitted from the light source to the optical recording medium and a reflected light beam from the optical recording medium, and receiving the reflected light beam separated by the light separating unit, A method of controlling the amplification circuit in an optical head, comprising: a photodetection unit that outputs a detection signal corresponding to the light intensity of the reflected light beam; and an amplification circuit that amplifies the detection signal. Is less than or equal to a predetermined threshold, the amplification factor of the amplification circuit is set to the first amplification factor A1, and when the level of the detection signal exceeds the threshold value, the amplification factor of the amplification circuit is increased by the first amplification factor A1. Second amplification factor of a value lower than the rate A2
It is characterized by Therefore, according to the control method of the amplifier circuit in the optical head of the present invention, when the light intensity of the light beam emitted from the light source is low, the detection signal is amplified with the amplification factor A1 and the light beam emitted from the light source is amplified. When the light intensity is high, the detection signal is amplified with an amplification factor A2 lower than the amplification factor A1.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an optical head, a recording / reproducing apparatus and a control method of an amplifier circuit in the optical head according to the present invention will be described below in detail with reference to the drawings. Figure 2
FIG. 3 is a block diagram showing a configuration of an optical disc recording / reproducing apparatus incorporating the optical head according to the first embodiment of the present invention. The optical disc recording / reproducing apparatus shown in FIG.
It is an example of a recording / reproducing apparatus capable of mounting an optical head described below. The optical head is for reproducing a CD, C
It is configured to record and reproduce D-R.

In FIG. 2, the recording / reproducing apparatus 101 is shown.
Is provided with a spindle motor 103 as a drive unit for rotating and driving an optical disc 102 as an optical recording medium, an optical head 104, and a feed motor 105 as a drive unit. In this example, the optical disc 102 includes a CD and a CD-R. Here, the spindle motor 10
3 is driven and controlled by the system controller 107 and the servo control circuit 109. The rotation of the optical disk 102 is switched to N times speed (for example, 4 times speed, 8 times speed, 16 times speed, 24 times speed, 32 times speed) which is N times (N is a positive number) rotation speed based on 1 times speed. .

Signal modulator / demodulator and ECC block 108
Performs signal modulation, demodulation, and addition of ECC (error correction code). The optical head 104 has a signal modulation and ECC
The optical disc 1 that rotates according to the command of the block 108
The signal recording surface 02 is irradiated with light. Recording on the optical disc 102 by such light irradiation,
Playback is performed. As will be described later, the optical head 104 is configured to function as a reproducing optical head that irradiates a track on the signal recording surface of the optical disc 102 with a reproducing light beam when reproducing a CD or a CD-R.
It is configured to function as a recording optical head that irradiates a recording light beam onto a track on the signal recording surface of the optical disc 102 during recording of a CD-R.

The optical head 104 is the optical disk 10
Optical detecting means (not shown) for detecting the reflected light beam reflected from the signal recording surface of No. 2 and outputting a detection signal corresponding to the light intensity of the light beam, and a focus error signal and a tracking error based on the detection signal. And a preamplifier section 120 that generates a signal, an RF signal, a speed detection signal, and the like. The light detecting means and the preamplifier section 120 are incorporated in a PDIC (photodetector IC) 5 (see FIG. 3) described later. The detailed configuration and operation of the PDIC 5 will be described later. Then, according to the type of the recording medium to be reproduced, the servo control circuit 109, the signal modulation and ECC block 108, etc. perform predetermined demodulation and error correction processing based on the signal output from the preamplifier 120. Processing is performed. As a result, the demodulated recording signal is sent to the external computer 130 or the like via the interface 111 if it is for data storage of a computer, for example. As a result, the external computer 130 and the like can receive the signal recorded on the optical disc 102 as a reproduction signal.

For audio / visual use, digital / analog conversion is performed by the D / A conversion unit of the D / A and A / D converter 112, and the result is supplied to the audio / visual processing unit 113. Then, audio / video signal processing is performed by the audio / visual processing unit 113, and the audio / video signal is transmitted to an external imaging / projection device via the audio / visual signal input / output unit 114. A feed motor 105 for moving the optical head 104 to a predetermined recording track on the optical disc 102 is connected to the optical head 104. The servo control circuit 10 controls the spindle motor 103, the feed motor 105, and the focusing and tracking directions of the biaxial actuator that holds the objective lens of the optical head 104.
9 is performed. The control of the focusing direction and the tracking direction by the servo control circuit 109 and the control of the spindle motor 103 are performed by the preamplifier 120.
It is performed based on the detection signal amplified in.

Further, the laser control section 121 includes the optical head 1
The control unit 04 controls the laser light source, and switches the output power of the laser light source, that is, the intensity of the light beam emitted from the laser light source. Specifically, the laser controller 121 controls the optical disc 102.
Is configured so that it can be switched between a reproduction-use light intensity necessary for reproducing the information recorded on the optical disc and a recording-time intensity higher than the reproduction-time light intensity required for recording information on the optical disc. ing. Further, since the rotation of the optical disc 102 is switched to N times speed which is N times (N is a positive number) rotation speed based on 1 times speed as a reference, the intensity of the light beam emitted from the laser light source is changed to the N times speed. It is configured to be variable according to the numerical value of.

FIG. 3 is a block diagram showing the optical system of the optical head according to the first embodiment of the present invention. In FIG.
The optical head 104 includes a laser light source 1, a prism (light separating means) 2, a collimator lens 3, an objective lens (light collecting means) 4 and the PDIC 5, and each of these optical parts is mounted on a holder (not shown). Is configured.

The laser light source 1 is configured to emit a light beam B toward the prism 2. The optical head 104 outputs a plurality of light beams in order to obtain an error signal necessary for servo control.
In the case of the configuration in which the laser beam is irradiated on two, it goes without saying that the light beam B emitted from the laser light source 1 may be separated into a plurality of beams by using a grating element or the like. In this example, for simplification of description, the means for generating a plurality of light beams will be omitted.

The prism 2 transmits the light beam from the laser light source 1 and guides it to the collimator lens 3 and the objective lens 4, and is reflected by the optical disk 102 to pass through the objective lens 4 and the collimator lens 3. The reflected light beam is separated from the light beam incident from the laser light source 1 and reflected toward the PDIC 5.

The collimator lens 3 is configured to collimate the light beam emitted from the laser light source 1 and emit it as parallel light. The objective lens 4
Is the light beam B incident from the collimator lens 3.
Is condensed and applied to the signal recording layer of the optical disc 102, and the reflected light beam reflected from the optical disc 102 is emitted toward the collimator lens 3.

FIG. 1 is a circuit diagram showing an amplifier circuit which constitutes the preamplifier section 120 provided in the PDIC 5. The PDIC 5 is provided with an amplifier circuit corresponding to each of a plurality of detection signals (reproduction signal, force error signal, tracking error signal, speed detection signal) output from the photodetection means. Then 1
The two amplifier circuits will be described. As shown in FIG. 1, the amplifier circuit 20 constitutes a so-called current-voltage conversion circuit, and includes an amplifier 22, a first feedback resistor 24, a second feedback resistor 26, and a Zener diode 28. ing. The amplifier 22 has an inverting input terminal for receiving a detection signal (input current IIN) from a photodetector (PD) 30 that constitutes the photodetector, and a predetermined voltage VC.
And the output signal (output voltage V
And an output terminal for outputting (OUT).

Both ends of the first feedback resistor 24 are connected between the inverting input terminal and the output terminal of the amplifier 22. The second feedback resistor 26 has one end connected to the inverting input terminal of the amplifier 22 and the other end connected to the anode of the Zener diode 28.
The cathode of the Zener diode 28 is connected to the output terminal of the amplifier 22. As a result, the Zener diode 28 is provided so that a voltage opposite to the polarity of the Zener diode 28 is applied. The second feedback resistor 26 and the Zener diode 28 connected in series form a feedback circuit 29. As a result, the first feedback resistor 24 and the feedback circuit 29 are connected in parallel between the inverting input terminal and the output terminal of the amplifier 22. Therefore, when the voltage applied to the Zener diode 28 is equal to or lower than the breakdown voltage of the Zener diode 28, the Zener diode 28 is turned off, so that the amplification factor A1 of the amplifier circuit 20 (first The amplification factor) is determined by the resistance value R1 of the first feedback resistor 24.

When the voltage applied to the Zener diode 28 exceeds the breakdown voltage, the Zener diode 28 is turned on.
The amplification factor A2 (second amplification factor) of the amplifier circuit 20 is determined by the combined resistance value R12 of the resistance values R1 and R2 of the first and second feedback resistors 22 and 24. The resistance value R1
Is naturally smaller than the combined resistance value R12, the amplification factor A2 is reduced compared to the amplification factor A1 of the amplification circuit 20.
In the present embodiment, the first feedback resistor 2
4 and the feedback circuit 29 constitute the amplification factor control means described in the claims.

Next, the operation of the amplifier circuit 20 will be described with reference to FIG. FIG. 4 is a characteristic diagram showing the amplification characteristic of the amplifier circuit 20. The horizontal axis represents the input light amount PIN of the reflected light beam input to the photodetector 30, and the vertical axis represents the output voltage VOUT of the amplifier circuit 20. I am taking it. Further, the saturation level VS on the vertical axis represents the level of the output voltage at which the output of the amplifier 22 of the amplifier circuit 20 is saturated and the SN ratio deteriorates. As shown in FIG. 4, the input light amount P
Reference numeral 1 denotes the input light amount when reproducing the optical disc 102, input light amount P2 denotes the input light amount at the 8 × speed when recording the optical disc 102, and input light amount P4 denotes the input light amount at the 24 × speed when recording the optical disc 102. A solid line L1 shows the amplification characteristic of the amplification circuit 20, and a broken line L2 shows the amplification characteristic of the comparison target amplification circuit 100 described later.

The first amplification factor A1 of the amplifier circuit 20 is set so that an output signal of an appropriate output voltage V1 can be obtained corresponding to the input light amount P1 at the time of reproduction, and When the amount of input light exceeds the amount of input light P1, the Zener diode 28 is turned on, so that the second amplification factor A2 is set so that the output voltage VOUT becomes less than the saturation level VS. Therefore, in the amplifier circuit 20, when the input light quantity exceeds P1, the Zener diode 2
The voltage applied to 8 exceeds the breakdown voltage of the Zener diode 28. That is, the amplification factor of the amplifier circuit 20 is controlled when the voltage applied to the Zener diode 28 is equal to or lower than the breakdown voltage (in other words, the level of the detection signal of the photodetector of the PDIC 5 is equal to or lower than a predetermined threshold value). When the voltage applied to the Zener diode 28 exceeds the breakdown voltage (in other words, when the level of the detection signal exceeds the threshold value), The amplification factor A2 is lower than the amplification factor A1.

FIG. 7 is a circuit diagram of an amplifier circuit for comparison and comparison. The amplifier circuit 100 of FIG. 7 corresponds to the amplifier circuit 20 of FIG. 1 from which the feedback circuit 29 is removed.
The same parts as those of the amplifier circuit of 1 are given the same reference numerals.
As shown in FIG. 7, the amplification factor of the amplifier circuit 100 is determined by the resistance value R1 of the feedback resistor 24.

In the amplifier circuit 100 shown in FIG.
When the resistance value R1 of the feedback resistor 24 of the amplifier circuit 100 is set so as to obtain an output signal of an appropriate output voltage V1 corresponding to the input light amount P1 at the time of reproduction as indicated by a broken line L2 of FIG. When the rotation speed is increased to 8 times speed or 24 times speed, the light intensity of the light beam emitted from the laser light source 1 is switched so as to be increased, whereby the output voltage VOUT is also increased to the saturation level VS.
If it exceeds, the SN ratio of the output signal deteriorates.
On the other hand, as shown by the broken line L3 in FIG. 4, when the resistance value R1 of the feedback resistor 24 of the amplifier circuit 100 is set so that an output signal below the saturation level VS can be obtained even at 24 times speed, for example, reproduction is performed. When the amount of input light is small as at times, the light intensity of the light beam emitted from the laser light source 1 decreases, and the output voltage VOUT also greatly falls below the appropriate output voltage V1, which is preferable as an output signal. I can't say.

FIG. 5 is a waveform diagram showing an example of the waveform of the output signal of the amplifier circuit at the time of recording on the optical disk, where the horizontal axis represents time T and the vertical axis represents the output voltage VOUT. As shown in FIG. 5, in the recording of the optical disc, the recording period TW in which the light intensity of the light beam of the laser light source 1 is maintained at the recording level and the light intensity of the light beam of the laser light source 1 is set to the reproduction level. The reproduction period TR for maintaining the lowered state is alternately repeated. The recording period TW
Then, recording is performed on the recording layer of the optical disk, and during the reproduction period TR, control such as focus servo, tracking servo, and rotation speed servo is performed based on the focus error signal, tracking error signal, and speed detection signal. As shown in FIG. 5, according to the present embodiment, the output voltage VOUT is maintained below the saturation level VS by switching the amplification factor of the amplification circuit 20 to A1 in the recording period TW, and Reproduction period T
In R, the amplification factor of the amplifier circuit 20 is switched to A2 so that it is controlled to be an appropriate output voltage V1 or higher.

As described in detail above, according to the first embodiment, it is possible to amplify the detection signal output from the photodetection means at an appropriate amplification factor during reproduction of the optical disc, regardless of the rotation speed of the optical disc. Moreover, at the time of recording on the optical disc, the detection signal output from the photodetector can be amplified with an appropriate amplification factor that does not saturate the amplifier circuit, and an output signal with a good SN ratio can always be obtained. Further, since the changeover switch and the control signal for controlling the changeover switch are not required for controlling the amplification factor of the amplifier circuit, the configuration can be simplified and the circuit can be downsized and the cost can be reduced. Is advantageous.

Next, a second embodiment will be described.
FIG. 6 is a circuit diagram of the amplifier circuit according to the second embodiment. As shown in FIG. 6, the amplifier circuit 20A of the second embodiment differs from the amplifier circuit 20 of the first embodiment in that a diode is provided instead of the Zener diode. The amplifier circuit 20A constitutes a current-voltage conversion circuit as in the first embodiment,
Amplifier 22, first feedback resistor 24, second feedback resistor 2
6 and the diode 28A. The amplifier 22 has an inverting input terminal for inputting a detection signal (input current IIN) from a photodetector (PD) 30 constituting the photodetector, a non-inverting input terminal held at a predetermined voltage VC, and an output signal ( And an output terminal for outputting the output voltage VOUT).

Both ends of the first feedback resistor 24 are connected between the inverting input terminal and the output terminal of the amplifier 22. The second feedback resistor 26 has one end connected to the inverting input terminal of the amplifier 22 and the other end connected to the cathode of the diode 28. The anode of the diode 28 is connected to the output terminal of the amplifier 22. As a result, the diode 28 is provided so that a voltage in the same direction as the polarity of the diode 28 is applied. The feedback circuit 2 is connected by the second feedback resistor 26 and the diode 28 connected in series.
9A is configured. As a result, the first feedback resistor 2 is provided between the inverting input terminal and the output terminal of the amplifier 22.
4 and the feedback circuit 29 are connected in parallel. Therefore, when the voltage applied to the diode 28 is equal to or lower than the forward voltage of the diode 28A, the diode 28A is turned off, so that the amplification factor A1 (first amplification factor) of the amplification circuit 20A. Is the first
Is determined by the resistance value R1 of the feedback resistor 24.

When the voltage applied to the diode 28A exceeds the forward voltage, the diode 28A is turned on, so that the amplification factor A2 (second amplification factor) of the amplification circuit 20 is reached. Is the first and second feedback resistors 2
It is determined by the combined resistance value R12 of the resistance values R1 and R2 of 2, 24. Since the resistance value R1 is naturally smaller than the combined resistance value R12, the amplification factor A2 decreases as compared with the amplification factor A1 of the amplification circuit 20A. It should be noted that in the present embodiment, the first feedback resistor 24 and the feedback circuit 29 are provided.
A constitutes the amplification factor control means described in the claims.

Therefore, in the amplifier circuit 20A, the voltage applied to the diode 28A exceeds the forward voltage of the diode 28A when the input light quantity exceeds P1. That is, the amplification factor of the amplifier circuit 20 is controlled when the voltage applied to the diode 28A is equal to or lower than the forward direction (in other words, the level of the detection signal of the photodetector of the PDIC 5 is equal to or lower than a predetermined threshold value). When), the amplification factor A1
Therefore, when the voltage applied to the diode 28A exceeds the forward voltage (in other words, when the level of the detection signal exceeds the threshold value), the amplification factor A2 lower than the amplification factor A1 is obtained. Has been done.

Also in the second embodiment as described above,
Similar to the first embodiment, regardless of the rotation speed of the optical disc, the detection signal output from the photodetector can be amplified with an appropriate amplification factor when the optical disc is reproduced, and the optical signal is recorded when the optical disc is recorded. The detection signal output from the detection means can be amplified with an appropriate amplification factor such that the amplification circuit does not saturate, and an output signal with a good SN ratio can always be obtained. Further, since the changeover switch and the control signal for controlling the changeover switch are not required for controlling the amplification factor of the amplifier circuit, the configuration can be simplified and the circuit can be downsized and the cost can be reduced. Is advantageous. In the first and second embodiments described above, the case where the CD or CD-R is used as the optical recording medium has been described, but the optical recording medium is not limited to these, and for example, the CD-RW. Needless to say, the present invention can be applied to optical discs such as MD, DVD, and DVD-RW.

[0031]

As described above, the optical head of the present invention,
According to the recording / reproducing apparatus and the control method of the optical head, the amplification degree of the detection signal of the reflected light beam can be appropriately controlled according to the increase and decrease of the light intensity of the light beam.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an amplifier circuit of an optical head according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an optical disc recording / reproducing apparatus incorporating the optical head according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram showing an optical system of the optical head according to the first embodiment of the invention.

FIG. 4 is a characteristic diagram showing amplification characteristics of the amplifier circuit according to the first embodiment of the present invention.

FIG. 5 is a waveform diagram showing an example of the waveform of the output signal of the amplifier circuit during recording on the optical disc.

FIG. 6 is a circuit diagram of an amplifier circuit according to a second embodiment.

FIG. 7 is a circuit diagram of an amplifier circuit for comparison and comparison.

[Explanation of symbols]

1 ... Laser light source, 2 ... Prism, 3 ... Collimator lens, 4 ... Objective lens, 5 ... PDIC, 20 ...
Amplifier circuit, 22 ... Amplifier, 24 ... First feedback resistor,
26 ... Second feedback resistor, 28 ... Zener diode, 28A ... Diode, 29, 29A ... Feedback circuit, 104 ... Optical head.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5D118 AA01 AA03 AA14 BA01 BB01                       BB03 BB06 BB07 CD02 CD03                       CD17                 5D119 AA06 AA12 AA28 BA01 BB01                       BB02 BB04 BB05 DA01 DA05                       EA02 EA03 EC18 KA43                 5D789 AA06 AA12 AA28 BA01 BB01                       BB02 BB04 BB05 DA01 DA05                       EA02 EA03 EC18 KA43

Claims (20)

[Claims] 1. A light source that emits a light beam, a light condensing unit that condenses the light beam emitted from the light source and irradiates the optical recording medium, and condenses the light beam emitted from the light source. And a light separating means for separating a light beam emitted from the light source to the optical recording medium and a reflected light beam from the optical recording medium, and the light separating means. An optical head comprising: a photodetector that receives the separated reflected light beam and outputs a detection signal corresponding to the light intensity of the reflected light beam; and an amplifier circuit that amplifies the detection signal. Amplification factor control means for controlling the amplification factor is provided, and the amplification factor control means controls the amplification factor such that the amplification factor is the first amplification factor A1 when the level of the detection signal is equal to or lower than a predetermined threshold value. And the above Output level of the signal when it exceeds the threshold value is performed such that the second amplification factor A2 of the first value lower than the amplification factor, the optical head, characterized in that. 2. The amplifier circuit includes an amplifier having an inverting input terminal to which the detection signal is input, a first feedback resistor connected between the inverting input terminal and an output terminal of the amplifier, and A first feedback resistor and a feedback circuit connected in parallel, the feedback circuit having a second feedback circuit connected in series with each other;
Feedback resistor and a Zener diode, the Zener diode is provided so that a voltage in the opposite direction to the polarity of the Zener diode is applied, and the amplification factor control means is configured by the first feedback resistor and the feedback circuit. The optical head according to claim 1, wherein: 3. The amplification factor of the amplifier circuit is determined by the resistance value of the first feedback resistor when the voltage applied to the Zener diode is equal to or lower than the breakdown voltage of the Zener diode, When the voltage applied to the diode exceeds the breakdown voltage of the Zener diode, the amplification factor of the amplifier circuit is determined by the combined resistance value of the first and second feedback resistors. The optical head according to claim 2. 4. The amplifier circuit includes an amplifier having an inverting input terminal to which the detection signal is input, a first feedback resistor connected between the inverting input terminal and an output terminal of the amplifier, and A first feedback resistor and a feedback circuit connected in parallel, the feedback circuit having a second feedback circuit connected in series with each other;
Feedback resistance and a diode, the diode is provided so that a voltage in the same direction as the polarity of the diode is applied, and the amplification factor control means is configured by the first feedback resistance and the feedback circuit. The optical head according to claim 1, wherein: 5. When the voltage applied to the diode is equal to or lower than the forward voltage of the diode, the amplification factor of the amplifier circuit is determined by the resistance value of the first feedback resistor and applied to the diode. 5. When the applied voltage exceeds the forward voltage of the diode, the amplification factor of the amplifier circuit is determined by the combined resistance value of the first and second feedback resistors. Light head. 6. The detection signal amplified by the amplifier circuit performs servo control of a reproduction signal of information recorded on the optical recording medium and a focus direction of the optical recording medium and the light focusing means. A focus error signal for tracking, a tracking error signal for performing servo control in the tracking direction of the optical recording medium and the light focusing means, and a speed detection signal for performing servo control of the rotation speed of the optical recording medium. The optical head according to claim 1, which is a signal for generating at least one signal of 7. The light source controls the intensity of a light beam emitted from the light source, the reproduction light intensity necessary for reproducing information recorded on the optical recording medium, and the information on the optical recording medium. It is configured to be switched to a recording intensity that is higher than the reproduction light intensity necessary for recording, and the amplification factor control means controls the amplification factor such that the intensity of the light beam is the reproduction intensity. 2. The optical head according to claim 1, wherein the output signal of the amplifier circuit is so set as not to be saturated when switched between the recording intensity and the recording intensity. 8. The optical recording medium is reproduced and recorded by being irradiated with the light beam in a rotated state, and the rotation of the optical recording medium is N times (N: The rotation speed is a positive number) and is switched to N times speed, and the intensity of the light beam emitted from the light source is configured to be variable according to the numerical value of N, and the amplification by the amplification factor control means is performed. The optical head according to claim 1, wherein the control of the rate is performed so that the output signal of the amplifier circuit is not saturated regardless of the value of N. 9. A drive means for holding and rotating the optical recording medium, and an optical recording medium rotationally driven by the driving means,
An optical head that emits light and detects reflected light from the optical recording medium, and a reproduction signal processing circuit that generates a reproduction signal based on a detection signal from the optical head are provided. A light source that emits a beam, a light condensing unit that condenses the light beam emitted from the light source and irradiates the optical recording medium, a light beam emitted from the light source to the optical recording medium, and the optical recording Light separating means for separating the reflected light beam from the medium, and light detecting means for receiving the reflected light beam separated by the light separating means and outputting a detection signal corresponding to the light intensity of the reflected light beam. In a recording / reproducing apparatus including an amplification circuit that amplifies the detection signal, an amplification factor control unit that controls the amplification factor of the amplification circuit is provided, and the amplification factor control unit controls the amplification factor by the detection signal. Level Is equal to or smaller than a predetermined threshold value, the amplification factor becomes the first amplification factor A1, and when the level of the detection signal exceeds the threshold value, the second amplification factor is lower than the first amplification factor. A recording / reproducing apparatus characterized in that the recording / reproducing apparatus is performed so as to have a rate A2. 10. The amplifier circuit includes an amplifier having an inverting input terminal to which the detection signal is input, a first feedback resistor connected between the inverting input terminal and an output terminal of the amplifier, and A first feedback resistor and a feedback circuit connected in parallel, wherein the feedback circuit comprises a second feedback resistor and a Zener diode connected in series with each other, and the Zener diode is opposite to the polarity of the Zener diode. 10. The recording / reproducing apparatus according to claim 9, wherein the recording / reproducing apparatus is provided so that the voltage of 1) is applied, and the amplification factor control means is constituted by the first feedback resistor and a feedback circuit. 11. The amplification factor of the amplifier circuit is determined by the resistance value of the first feedback resistor when the voltage applied to the Zener diode is equal to or lower than the breakdown voltage of the Zener diode. When the voltage applied to the diode exceeds the breakdown voltage of the Zener diode, the amplification factor of the amplifier circuit is determined by the combined resistance value of the first and second feedback resistors. The recording / reproducing apparatus according to claim 10. 12. The amplifier circuit includes an amplifier having an inverting input terminal to which the detection signal is input, a first feedback resistor connected between the inverting input terminal and an output terminal of the amplifier, and A first feedback resistor and a feedback circuit connected in parallel, wherein the feedback circuit comprises a second feedback resistor and a diode connected in series with each other, and the diode has a voltage in the same direction as the polarity of the diode. 10. The recording / reproducing apparatus according to claim 9, wherein the recording / reproducing apparatus is provided so as to be applied, and the amplification factor control means is constituted by the first feedback resistor and a feedback circuit. 13. When the voltage applied to the diode is equal to or lower than the forward voltage of the diode, the amplification factor of the amplifier circuit is determined by the resistance value of the first feedback resistor and applied to the diode. 13. The amplification factor of the amplifier circuit is determined by the combined resistance value of the first and second feedback resistors when the applied voltage exceeds the forward voltage of the diode. Recording and reproducing device. 14. The detection signal amplified by the amplifier circuit performs a servo control of a reproduction signal of information recorded on the optical recording medium and a focus direction of the optical recording medium and the light focusing means. A focus error signal for tracking, a tracking error signal for performing servo control in the tracking direction of the optical recording medium and the light focusing means, and a speed detection signal for performing servo control of the rotation speed of the optical recording medium. 10. The recording / reproducing apparatus according to claim 9, wherein the recording / reproducing apparatus is a signal for generating at least one of the signals. 15. The light source controls the intensity of a light beam emitted from the light source, the reproduction light intensity necessary for reproducing information recorded on the optical recording medium, and the information on the optical recording medium. It is configured to be switched to a recording intensity that is higher than the reproduction light intensity necessary for recording, and the amplification factor control means controls the amplification factor such that the intensity of the light beam is the reproduction intensity. 10. The recording / reproducing apparatus according to claim 9, wherein the recording / reproducing apparatus is performed so that the output signal of the amplifier circuit is not saturated when switched between the recording intensity and the recording intensity. 16. The optical recording medium is reproduced and recorded by being irradiated with the light beam in a rotated state, and the rotation of the optical recording medium is N times (N: The rotation speed is a positive number) and is switched to N times speed, and the intensity of the light beam emitted from the light source is configured to be variable according to the numerical value of N.
The control of the amplification factor by the amplification factor control means is performed by the N
10. The recording / reproducing apparatus according to claim 9, wherein the output signal of the amplifier circuit is so set as not to saturate regardless of the numerical value of. 17. A light source that emits a light beam, a light condensing unit that condenses the light beam emitted from the light source and irradiates the optical recording medium, and an optical recording medium emitted from the light source to the optical recording medium. A light separating means for separating a light beam and a reflected light beam from the optical recording medium, and the reflected light beam separated by the light separating means are received, and a detection signal corresponding to the light intensity of the reflected light beam is generated. A method for controlling the amplification circuit in an optical head comprising a photodetection unit for outputting and an amplification circuit for amplifying the detection signal, wherein the amplification circuit is provided when the level of the detection signal is below a predetermined threshold value. Is set to a first amplification factor A1, and when the level of the detection signal exceeds the threshold value, the amplification factor of the amplification circuit is set to a second amplification factor A2 which is lower than the first amplification factor. And that The method of amplifying circuit in the optical head according to symptoms. 18. The detection signal amplified by the amplifier circuit performs a servo control of a reproduction signal of information recorded on the optical recording medium and a focus direction of the optical recording medium and the light focusing means. A focus error signal for tracking, a tracking error signal for performing servo control in the tracking direction of the optical recording medium and the light focusing means, and a speed detection signal for performing servo control of the rotation speed of the optical recording medium. 18. The method for controlling an amplifier circuit in an optical head according to claim 17, which is a signal for generating at least one signal of 19. The light source controls the intensity of a light beam emitted from the light source, the reproduction light intensity necessary for reproducing information recorded on the optical recording medium, and the information on the optical recording medium. It is configured to be switched to a recording intensity of a value higher than the reproduction light intensity required for recording, and the amplification factor is controlled so that the intensity of the light beam is the reproduction intensity and the recording intensity. 18. The method of controlling an amplifier circuit in an optical head according to claim 17, wherein the output signal of the amplifier circuit is controlled so as not to be saturated when switched between the two. 20. A signal is reproduced and recorded by irradiating the optical beam on the optical recording medium in a rotated state, and the optical recording medium is rotated N times (N is a speed) with reference to 1 × speed. The rotation speed is a positive number) and is switched to N times speed, and the intensity of the light beam emitted from the light source is configured to be variable according to the numerical value of N.
18. The method of controlling an amplification circuit in an optical head according to claim 17, wherein the control of the amplification factor is performed so that the output signal of the amplification circuit is not saturated regardless of the value of N.