JP2006024323A - Optical disk apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that when light receiving output of a light receiving element for front monitor is reduced due to reduction of power source voltage, such control is performed that laser light quantity from a laser light source is increased by an APC(Automatic Power Control) circuit, and the apparatus is not controlled to laser light quantity being appropriate for recording or reproducing of a disk. <P>SOLUTION: Offset data of offset voltage of the APC circuit 9 corresponding to power source voltage applied to the light receiving element 4 for front monitor is previously stored in a memory circuit 12 for each optical disk apparatus conforming to a property of an optical head apparatus, when it is detected by a power source voltage detecting circuit 11 that the power source voltage applied to the light receiving element 4 for front monitor is reduced to the prescribed voltage, offset data corresponding to the prescribed voltage is read out from the memory circuit 12, offset voltage corresponding to reduction of the power source voltage of the light receiving element 4 for front monitor is set to the APC circuit 9. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, laser light emitted forward from the laser light source of the optical head device to the disk side is received by a light receiving element for front monitor, and the APC circuit uses the front monitor output output from the light receiving element for front monitor. The present invention relates to an optical disk device that controls the laser output from the laser light source to a constant light amount. Also, the laser light emitted from the laser light source of the optical head device is focused on the disk and irradiated, and the laser light reflected from the disk is emitted. Light is received by the detector, and each light receiving output obtained from each of the plurality of light receiving areas formed in the light detector is processed by a signal generation circuit to generate a disc information signal, a focus error signal, and a tracking error signal. The present invention relates to an optical disk device.

  As an optical disk apparatus for recording on a disk using laser light from an optical head apparatus, a CD-R (Recordable) and CD-RW (ReWritable) recording system of CD (Compact Disc) standard, and a DVD (Digital Versatile Disc) Standard recording methods such as R and RW or RAM are well known.

  In an optical head device used in an optical disk device corresponding to such disk recording, a front monitor light receiving element is usually provided to directly receive a part of a laser beam emitted from a laser light source to the disk side. An optical disc apparatus equipped with an optical head device having a light receiving element for front monitor uses a light receiving output (front monitor output) of the light receiving element for front monitor, and a laser light source by a laser output control circuit having an APC (Automatic Power Control) circuit. The laser output is controlled so that the laser beam emitted from the laser beam is a constant light amount, so that the laser beam irradiated from the optical head device to the disk is kept constant at an appropriate light amount for recording and reproduction on the disk. It has become.

  Further, the optical head device is provided with a photodetector for receiving the laser light reflected from the disk, and the optical disk device performs arithmetic processing on each light receiving output obtained from each of a plurality of light receiving regions formed in the photodetector. A signal generation circuit that generates a disc information signal, a focus error signal, a tracking error signal, or a tilt signal as necessary is provided.

  The optical head device is equipped with an electrical component such as a semiconductor laser serving as a light source and a laser driving semiconductor integrated circuit for driving the semiconductor laser in addition to the above-described front monitor light receiving element and photodetector, and an objective lens. The actuator for driving is composed of a permanent magnet, a yoke, and various drive coils (a focus coil and a tracking coil, and a tilt coil as required), and a drive signal is supplied to the various drive coils.

  In the optical disk device, generally, the optical head device is supported so as to be movable in a direction crossing the signal track of the disk, and the optical head device and a circuit board installed in the apparatus main body of the optical disk device are flexible wiring boards. And a transmission cable such as a flat cable, and an electrical signal is exchanged between the optical head device and the circuit board using the transmission cable.

Incidentally, the APC circuit is provided with an offset adjustment circuit for adjusting the offset of the APC circuit in order to appropriately set the relationship between the light reception output of the front monitor light receiving element and the drive signal for driving the laser light source. (See Patent Document 1)
Further, in a laser output control circuit including an APC circuit, an offset compensation circuit is provided to compensate for a change in the offset of the APC circuit when the offset of the APC circuit changes due to a temperature change or a change with time of the laser light source. (See Patent Document 2)
Japanese Patent Laid-Open No. 5-128572 JP 2001-274504 A

  By the way, as an optical disk apparatus, there are a portable personal computer, a so-called slim type that is incorporated into a so-called notebook personal computer, or a stand-alone type that is connected to an external terminal of a personal computer. The power source usually uses a battery of a personal computer or an optical disk device itself.

  As described above, in an optical disc apparatus that uses a battery as a power source, the power supply voltage applied to the electrical components mounted on the optical head device also decreases as the power supply voltage of the optical disc apparatus decreases due to battery consumption.

  When the power supply voltage to the electrical components of the optical head device decreases, the light reception output of the front monitor light receiving element and the photodetector may decrease even if the power supply voltage is within the guaranteed operating range of the optical disk device.

  When the light reception output of the light receiving element for the front monitor is reduced, the APC circuit is controlled to increase the laser light amount from the laser light source in the same manner as when the light amount of the laser light emitted from the laser light source is reduced, and the disk recording or reproduction is performed. Therefore, it becomes impossible to control the laser light amount appropriately.

  Further, when the light receiving output of the photodetector is lowered, there is a concern that the S / N of the light receiving output is lowered, or necessary signal generation cannot be performed correctly.

  The invention according to claim 1 is set in the APC circuit in accordance with a power supply voltage detection circuit for detecting that the power supply voltage applied to the light receiving element for front monitor drops to a predetermined voltage, and a detection output by the power supply voltage detection circuit. An offset voltage adjusting circuit for adjusting the offset voltage to be applied, and a memory circuit for storing offset data corresponding to the offset voltage set in the APC circuit corresponding to the power supply voltage applied to the light receiving element for front monitor; The offset data of the offset voltage of the APC circuit corresponding to the power supply voltage applied to the front monitor light receiving element is stored in advance in the memory circuit for each optical disk device in accordance with the characteristics of the optical head device. The power supply voltage applied to the light receiving element for front monitor is lowered to a predetermined voltage by the voltage detection circuit There has been to set the offset voltage corresponding to a decrease in reading the offset data corresponding to the predetermined voltage from said memory circuit when the detected power supply voltage of the front monitor light receiving element to the APC circuit.

According to a third aspect of the present invention, there is provided a level setting circuit for setting each light receiving output obtained from each light receiving region of the photodetector to an appropriate voltage level for the signal generation circuit, and a power supply voltage applied to the photodetector is predetermined. A power supply voltage detection circuit for detecting a drop in voltage, an offset adjustment circuit for adjusting an offset voltage set in the level setting circuit in accordance with a detection output by the power supply voltage detection circuit, and applied to the photodetector. A memory circuit that stores offset data corresponding to an offset voltage set in the level adjustment circuit corresponding to the power supply voltage to be applied, and the power supply voltage applied to the photodetector by the power supply voltage detection circuit is a predetermined voltage. In response to a decrease in the power supply voltage of the photodetector by reading offset data corresponding to the predetermined voltage from the memory circuit The offset voltage is to set the level setting circuit.

  According to the first aspect of the present invention, when the power supply voltage applied to the light receiving element for front monitor is lowered to a predetermined voltage, the offset data corresponding to the predetermined voltage is read from the memory circuit and the offset corresponding to the offset data is read. Since the voltage is set in the APC circuit, the offset voltage of the APC circuit is set so as to compensate for the decrease in the light reception output of the light receiving element for the front monitor, and the laser light from the laser light source is suitable for disk recording or reproduction. The amount of light can be controlled.

  According to the second aspect of the present invention, characteristic data indicating the relationship between the power supply voltage of the light receiving element for the front monitor and the light receiving output of the light receiving element for the front monitor is encoded in the data table provided in the optical head device. Since the offset data of the offset voltage of the APC circuit corresponding to the power supply voltage of the light receiving element for front monitor that is recorded and detected based on this characteristic data is stored in the memory circuit, the optical head device The front monitor light reception for the power supply voltage of each optical head device is based on the offset voltage of the APC circuit when the power supply voltage is lowered to a predetermined voltage based on the measured value indicating the relationship of the light reception output of the front monitor light reception element to the power supply voltage for each The front monitor is set based on the actual measurement value indicating the relationship between the light reception outputs of the elements and is caused by a drop in power supply voltage. You can compensate for lowering of the light receiving outputs of use the light receiving element.

  According to the third aspect of the present invention, when the power supply voltage applied to the photodetector is lowered to a predetermined voltage, the offset data corresponding to the predetermined voltage is read from the memory circuit and the offset corresponding to the offset data is read. Since the voltage is set in the level setting circuit that adjusts the voltage level of each light receiving output of the photodetector, the offset voltage of the level setting circuit is set to compensate for the decrease in each light receiving output of the photodetector. Each light receiving output of the photodetector obtained through the setting circuit can be held at an appropriate level.

  According to claim 4 of the present invention, the characteristic data indicating the relationship between the power supply voltage of the photodetector and the light reception output of the photodetector is encoded and recorded in the data table provided in the optical head device. Since the offset data of the offset voltage of the level setting circuit corresponding to the power supply voltage of the photodetector detected based on this characteristic data is stored in the memory circuit, the power supply voltage is lowered to a predetermined voltage. The offset voltage of the level setting circuit at the time is set based on the actual measurement value indicating the relationship of the light reception output of the photodetector with respect to the power supply voltage for each optical head device, and the light reception output of the photodetector decreases due to the decrease of the power supply voltage. Can be compensated.

  FIG. 1 is a circuit block diagram showing a first embodiment showing a semiconductor laser drive system of an optical head device of an optical disk apparatus according to the present invention. This optical disk apparatus has a configuration corresponding to a CD and a DVD.

  In FIG. 1, only one for CD or DVD is shown, but the circuit having the configuration shown in FIG. 1 is prepared for both CD and DVD, so that the semiconductor laser for CD and the semiconductor laser for DVD are used. The light emission output of each laser beam emitted is controlled.

The laser diode 1 of the semiconductor laser is driven according to the drive signal output from the laser drive circuit 2 and emits laser light. The laser driving circuit 2 is controlled by a laser control circuit 3, and the laser control circuit 3 generates a pulsed recording driving signal based on the recording data set at an appropriate level according to the recording condition at the time of recording, and at the time of reproduction. A reproduction drive signal having a constant level set to an appropriate level according to the reproduction condition is generated.

  The laser light emitted by the laser diode 1 is received by the front monitor diode 4 of the front monitor light receiving element, and a light receiving current corresponding to the amount of the received laser light flows through the front monitor diode 4. The received light current is converted into a received light voltage of a voltage signal by a current-voltage conversion (I / V) circuit 5, smoothed by a low-pass filter (LPF) 6, and input to a differential amplifier 7.

  Since the offset voltage set by the offset setting circuit 8 is applied to the differential amplifier 7 as a reference voltage for comparison, the differential amplifier 7 receives the light reception voltage which is the front monitor output of the front monitor diode 4 via the LPF 6. And a differential voltage corresponding to the difference between the offset voltage and the offset voltage.

  This differential voltage is supplied to the laser control circuit 3, and the laser control circuit 3 controls the drive voltage generated from the laser drive circuit 2 in accordance with the differential voltage. As a result, a drive signal for driving the laser diode 1 is output from the laser drive circuit 2 so as to control the laser output of the laser diode 1 to a constant light amount. In this case, the recording drive signal is formed in a pulse shape by combining the signals of the respective power levels, but the reference power level signal among the signals of the respective power levels is controlled by the laser control circuit 3 to a constant light amount. Is done.

  The LPF 6, the differential amplifier 7, the offset setting circuit 8, and the laser control circuit 3 constitute an APC circuit 9 that controls the drive signal of the laser diode 1 according to the front monitor output.

  Here, the offset voltage set by the offset setting circuit 8 is set so that the relationship between the amount of light received by the front monitor diode 4 and the drive signal from the laser drive circuit 2 is appropriate. When a disc is played, a default value is set in advance as a reference in accordance with the playback conditions.

  By the way, the offset voltage set by the offset setting circuit 8 is adjusted by the offset adjustment circuit 10, and the offset adjustment circuit 10 supplies power to the front monitor diode 4 by the power supply voltage detection circuit 11. When it is detected that the voltage drops to a predetermined voltage, an offset voltage corresponding to the predetermined voltage is set in the offset setting circuit 8.

  The offset voltage set in the offset setting circuit 8 is based on offset data read from the memory circuit 12 constituted by an EEPROM which is an electrically rewritable ROM.

  In the memory circuit 12, the power supply voltage applied to the front monitor diode 4, offset data based on the offset voltage of the APC circuit 9 corresponding to the steady state and the predetermined voltage, respectively, are recorded on the optical disc in accordance with the characteristics of the optical head device. Pre-stored for each device.

  Therefore, when the power supply voltage applied to the front monitor diode 4 drops to a predetermined voltage, offset data corresponding to the predetermined voltage is read from the memory circuit 12 and the offset voltage corresponding to the offset data is supplied to the APC circuit 9. By setting, the offset voltage of the APC circuit 9 compensates for the decrease in the light reception output of the front monitor diode 4, and the light quantity of the laser light emitted from the laser diode 1 is maintained in an appropriate state for disk recording or reproduction. The

  Here, in the optical head device, a bar code or a two-dimensional code data table in which characteristic data indicating the relationship between the power supply voltage of the front monitor diode 4 and the light reception output of the front monitor diode 4 is individually coded. Is printed on the sticker.

  This data table is read by the reader device in the manufacturing process of the optical disk device, and the offset voltage of the APC circuit 9 corresponding to the power supply voltage of the front monitor diode 4 is detected based on the characteristic data recorded in this data table. Offset data corresponding to the voltage is stored in the memory circuit 12. Therefore, the offset set in the offset setting circuit 8 of the APC circuit 9 when the power supply voltage drops to a predetermined voltage based on the actual measurement value indicating the relationship between the light reception output of the front monitor diode 4 and the power supply voltage for each optical head device. The voltage is appropriately set corresponding to the variation of each optical head device.

  In the above-described embodiment, the point at which the drop in the power supply voltage is detected is set to a predetermined voltage. However, this predetermined voltage may be one point or a plurality of points. Although it increases, an appropriate offset voltage can be set in the offset setting circuit 8 in detail.

  FIG. 2 is a circuit block diagram showing a second embodiment showing a signal system of light reception output from the photodetector of the optical head device of the optical disk device according to the present invention, and this optical disk device has a configuration corresponding to CD and DVD. It has become.

  In the optical detector 20 that receives the reflected light from the disk of the optical head device, a CD light receiving unit used for recording / reproducing a CD and a DVD light receiving unit used for recording / reproducing a DVD are formed side by side on the same semiconductor substrate. ing.

  The CD light receiving unit includes a main light receiving region 21 for receiving the 0th order diffracted light of the laser light composed of each of the light receiving elements A, B, C, and D arranged in four crosses, and ± 1st order diffracted light of the laser light. The sub-light-receiving area is composed of E and F light-receiving elements 22 and 23 for receiving each sub-beam.

  On the other hand, the DVD light receiving unit is constituted by a main light receiving region 24 that receives the 0th-order diffracted light of the laser light composed of the light receiving elements a, b, c, and d arranged in a cross shape.

  Each light receiving output derived from the output terminals 25, 26, 27, 28 of the photodetector 20 is a selection switch 29 formed on the semiconductor substrate on which the CD light receiving unit and the DVD light receiving unit are formed. 30, 30, 31, and 32, and a light receiving output having a common signal type between the CD light receiving unit and the DVD light receiving unit is selectively derived.

  Each of the selection switches 29, 30, 31, and 32 selects a light receiving output of the CD light receiving unit or a light receiving output of the DVD light receiving unit according to a signal level applied to the switching control terminal 33.

  Therefore, by switching the signal level applied to the switching control terminal 33, the respective light receiving outputs of the CD light receiving unit and the DVD light receiving unit can be switched and derived from the output terminals 25, 26, 27, and 28 of the photodetector 20. The output terminals 25, 26, 27, and 28 are commonly used for CD recording and reproduction and DVD recording and reproduction. In this case, the light receiving outputs derived from the selection switches 29, 30, 31, and 32 are converted from current signals to voltage signals via current / voltage conversion circuits 34, 35, 36, and 37, respectively.

  The light receiving outputs from the light receiving elements 22 and 23 in the sub light receiving area of the CD light receiving unit are converted from current signals to voltage signals via current / voltage conversion circuits 38 and 39, respectively, and then output terminals 40, 41.

  Each light receiving output derived from each output terminal 25, 26, 27, 28, 40, 41 is supplied by a level setting circuit 42. The level setting circuit 42 adjusts the gain of each amplifier that amplifies each light receiving output. The offset voltage is applied so as to cancel the offset component of each amplifier, and the voltage level of each light receiving output is set so as to absorb the variation between the light receiving outputs.

  Each light receiving output whose voltage level has been set by the level setting circuit 42 is supplied to a signal generation circuit 43, which is processed by the signal generation circuit 43, equalized, and recorded on a recording mark (pit land) recorded on the disc. A corresponding RF signal (radio frequency signal) is generated, and a focus error signal (FE signal) indicating a focus shift from the disk signal surface of the laser beam that is processed by the signal generation circuit 43 and applied to the disk, and A tracking error signal (TE signal) indicating a tracking deviation of the laser beam from the signal track of the disk is generated.

  Here, in the CD, the astigmatism method is used to generate the focus error signal, and the three-beam method is used to generate the tracking error signal, while in the DVD, the astigmatism is used for focus control. As a method, a push-pull method is employed for tracking control, and the signal generation circuit 43 performs arithmetic processing according to these methods.

  By the way, the offset voltage set by the level setting circuit 42 is adjusted by the offset adjustment circuit 44, and the offset adjustment circuit 44 supplies power to the photodetector 20 by the power supply voltage detection circuit 45. When it is detected that the voltage drops to a predetermined voltage, an offset voltage corresponding to the predetermined voltage is set in the level setting circuit.

  The offset voltage set in the level setting circuit 42 is based on offset data read from a memory circuit 46 constituted by an EEPROM which is an electrically rewritable ROM.

  In the memory circuit 46, the power supply voltage applied to the photodetector 20, offset data based on the offset voltage of the level setting circuit 42 corresponding to the steady state and the predetermined voltage, respectively, according to the characteristics of the optical head device. Stored in advance for each optical disk device.

  Therefore, when the power supply voltage applied to the photodetector 20 is lowered to a predetermined voltage, the offset data corresponding to the predetermined voltage is read from the memory circuit 46, and the offset voltage corresponding to the offset data is changed to the level setting circuit 42. Therefore, the offset voltage of the level setting circuit 42 compensates for a decrease in each light receiving output of the photodetector 20, and each light receiving output of the photodetector 20 supplied to the signal generating circuit 43 is an RF signal, It is held at a voltage level appropriate for processing to generate FE and TE signals.

  Here, in the optical head device, bar code or two-dimensional code data in which characteristic data indicating the relationship between the power supply voltage of the light detector 20 and each light receiving output of the light detector 20 is coded and recorded individually. The table is printed on the sticker.

This data table is read by the reader device in the manufacturing process of the optical disk device, and the offset voltage of the level setting circuit 42 corresponding to the power supply voltage of the photodetector 20 is detected based on the characteristic data recorded in this data table. Offset data corresponding to the offset voltage is stored in the memory circuit 46. Therefore, the offset voltage set in the level setting circuit 42 when the power supply voltage drops to a predetermined voltage based on the actual measurement value indicating the relationship between the light receiving outputs of the photodetector 20 with respect to the power supply voltage for each optical head device is optical. It is set appropriately in accordance with the variation of each head device.

  In the above-described embodiment, the point at which the drop in the power supply voltage is detected is set to a predetermined voltage. However, this predetermined voltage may be one point or a plurality of points. Although the number is increased, an appropriate offset voltage can be set in the level setting circuit 42 in detail.

1 is a circuit block diagram showing a first embodiment showing a semiconductor laser drive system of an optical head device of an optical disk device according to the present invention. FIG. It is a circuit block diagram which shows the 2nd Example which shows the signal system of the light reception output from the photodetector of the optical head apparatus of the optical disk apparatus based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser diode 2 Laser drive circuit 3 Laser control circuit 4 Front monitor diode 7 Differential amplifier 8 Offset setting circuit 9 APC circuit 10 Offset adjustment circuit 11 Power supply voltage detection circuit 12 Memory circuit 20 Photo detectors 25, 26, 27, 28, 40, 41 Output terminal 42 Level setting circuit 43 Signal generation circuit 44 Offset adjustment circuit 45 Power supply voltage detection circuit 46 Memory circuit

Claims (4)

The APC circuit uses the front monitor output output from the front monitor light receiving element provided in the optical head device to monitor the laser output emitted from the laser light source of the optical head device to the front side of the disk. An optical disk apparatus for controlling the laser output of the light source to a constant light amount, a power supply voltage detection circuit for detecting that the power supply voltage applied to the light receiving element for front monitor drops to a predetermined voltage, and detection by the power supply voltage detection circuit An offset adjusting circuit for adjusting an offset voltage set in the APC circuit according to an output; and an offset corresponding to an offset voltage set in the APC circuit corresponding to a power supply voltage applied to the light receiving element for front monitor A memory circuit for storing data, and the memory circuit includes a front monitor. The offset data of the offset voltage of the APC circuit corresponding to the power supply voltage applied to the light receiving element for the optical disc is stored in advance for each optical disk device in accordance with the characteristics of the optical head device. The offset voltage corresponding to the decrease in the power supply voltage of the light receiving element for the front monitor by reading the offset data corresponding to the predetermined voltage from the memory circuit when it is detected that the power supply voltage applied to the voltage decreases to the predetermined voltage. Is set in the APC circuit. A data table in which characteristic data indicating the relationship between the power supply voltage of the front monitor light-receiving element and the light-receiving output of the front monitor light-receiving element is encoded is installed in the optical head device, and is mounted in the optical disk device manufacturing process. Read the data table of the head device, detect the offset voltage of the APC circuit corresponding to the power supply voltage of the light receiving element for front monitor based on the characteristic data described in this data table, and store the offset data corresponding to this offset voltage in the memory The optical disk apparatus according to claim 1, wherein the optical disk apparatus is stored in a circuit. The laser light emitted from the laser light source of the optical head device is condensed and irradiated on the disk, the laser light reflected from the disk is received by the photodetector, and a plurality of light receiving areas formed in the photodetector An optical disk apparatus that generates a disc information signal, a focus error signal, and a tracking error signal by performing arithmetic processing on each light reception output obtained from a signal generation circuit, and each light reception obtained from each light reception region of the photodetector A level setting circuit that sets an output to an appropriate voltage level for the signal generation circuit, a power supply voltage detection circuit that detects that a power supply voltage applied to the photodetector is lowered to a predetermined voltage, and the power supply voltage detection circuit An offset adjustment circuit for adjusting an offset voltage set in the level setting circuit in accordance with a detection output by the power supply, and an electric power applied to the photodetector. A memory circuit that stores offset data corresponding to an offset voltage set in the level adjustment circuit corresponding to the voltage, the level setting corresponding to the power supply voltage applied to the photodetector The offset data of the offset voltage of the circuit is stored in advance for each optical disk device in accordance with the characteristics of the optical head device, and the power supply voltage applied to the photodetector is detected by the power supply voltage detection circuit to a predetermined voltage. When the optical disc is read, offset data corresponding to the predetermined voltage is read from the memory circuit, and an offset voltage corresponding to a decrease in the power supply voltage of the photodetector is set in the level setting circuit. apparatus. A data table in which characteristic data indicating the relationship between the power supply voltage of the photodetector and the light reception output of the photodetector is encoded is set in the optical head device, and data of the optical head device mounted in the manufacturing process of the optical disc device Read the table, detect the offset voltage of the level setting circuit corresponding to the power supply voltage of the photodetector based on the characteristic data described in this data table, and store the offset data corresponding to this offset voltage in the memory circuit The optical disk apparatus according to claim 3.

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