JP2005243156A - Laser output setting method of optical disk recording or reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser output setting method of an optical disk recording or reproducing apparatus which can record a signal on a disk with an optical pickup. <P>SOLUTION: A relationship between a level of driving signal and a level of focus error signal which are supplied to a laser diode 3 included in the optical pickup is obtained, and the level of the driving signal to be supplied to the laser diode is set so as to emit the laser output to obtain the focus error signal of an established level. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser output setting method for an optical disc recording / reproducing apparatus configured to record a signal on a disc with a laser beam irradiated from an optical pickup and perform a reproduction operation of the signal recorded on the disc with the laser beam. About.

  An optical disk playback device that performs an operation of reading a signal recorded on a disk using an optical pickup is widely used. In addition to the playback function, a signal is recorded on the disk by a laser beam emitted from the optical pickup. An optical disc recording / reproducing apparatus configured so as to be capable of recording is commercially available.

  An optical disc recording / reproducing apparatus capable of recording a signal on a disc needs to accurately perform a focusing control operation for focusing the laser beam on the signal track of the disc and a tracking control operation for tracking the laser beam on the signal track. Each control operation is performed by using a focus error signal and a tracking error signal obtained from a photodetector incorporated in the optical pickup. Generally, such a control operation is performed by a focus servo circuit and a tracking. The servo circuit is configured to perform the servo operation.

Further, such an optical disc recording / reproducing apparatus is configured to perform signal recording operation by forming pits on the disc by laser beam irradiation operation, but it is necessary to make the pit shape conform to the disc standard. There is. In order to accurately perform the recording operation, it is necessary to control the output of the laser beam so that it becomes a set level. Conventionally, a monitoring element for monitoring the level of the laser beam emitted from the laser diode is provided. The output of the laser beam is adjusted using a monitor signal obtained from the monitor element (see, for example, Patent Document 1).
JP 2001-43552 A

  The control operation to focus the laser light emitted from the laser diode built into the optical pickup onto the signal surface on the disc is the focus error obtained from the photodetector built into the optical pickup as described above. This is performed by using a signal, that is, by a servo operation by a circuit called a focus servo circuit. The control operation for focusing the laser beam on the signal surface is performed by the servo operation of the focus servo circuit. To perform the control operation, the servo gain of the focus servo circuit needs to be set to an optimum value. There is.

  There is a problem that the servo gain adjustment setting operation of such a focus servo circuit cannot be performed accurately unless the output of the laser light emitted from the laser diode is at a predetermined level. When using an optical pickup that incorporates a monitoring element that monitors the level of laser light emitted from the laser diode, as in the technique described in the above-mentioned patent document, detection is performed by the monitoring element. Since the laser output can be adjusted to a predetermined value by feeding back the monitor signal, the servo gain setting operation of the focus servo circuit can be easily performed.

  On the other hand, in recent years, an optical pickup in which a monitoring element for monitoring the level of laser light emitted from a laser diode is deleted is sold in order to reduce the price of the optical pickup. In an optical disk recording / reproducing apparatus using such an optical pickup, a method of adjusting the laser output generally employs a method using the level of an RF signal obtained from laser light reflected from the disk.

  Such laser output adjustment operation is performed when the recording operation is performed by the optical disc recording / reproducing apparatus, but the gain setting operation of the focus servo circuit needs to be performed when the optical disc recording / reproducing apparatus is manufactured. . In the manufacturing process, in order to perform the gain setting operation of the focus servo circuit, it is necessary to set the laser output to a predetermined value. However, since laser diodes have large variations in laser output, they are accurately adjusted in the manufacturing process. There is a need to.

  The present invention is intended to provide a laser output setting method that is effective when the gain setting operation of a focus servo circuit is accurately performed.

  The present invention obtains the relationship between the level of a drive signal supplied to a laser diode incorporated in an optical pickup and the level of a focus error signal, and emits a laser output that can obtain a focus error signal of a set level. The level of the drive signal supplied to the laser diode is set.

  Further, the present invention is configured to set the gain of the focus servo circuit after the laser output setting operation is performed.

  Further, according to the present invention, the relationship between the level of the drive signal supplied to the laser diode and the level of the focus error signal is such that the focus error signal level is maximized in the focusing coil provided to move the objective lens in the disk surface direction. It is configured so as to be obtained by supplying a drive signal that changes until it reaches a minimum.

  The present invention obtains the relationship between the level of a drive signal supplied to a laser diode incorporated in an optical pickup and the level of a focus error signal, and emits a laser output that can obtain a focus error signal of a set level. Since the level of the drive signal supplied to the laser diode is set, the optical pickup that does not incorporate the monitoring element that monitors the level of the laser light emitted from the laser diode is used. The laser output setting operation can be performed accurately.

  In the present invention, since the gain of the focus servo circuit is set after the laser output is set, the gain setting operation of the focus servo circuit can be performed accurately.

  According to the present invention, the level of the focus error signal is applied to the focusing coil provided to move the objective lens in the direction of the disk surface based on the relationship between the level of the drive signal supplied to the laser diode and the level of the focus error signal. Since the drive signal that changes from the maximum to the minimum is supplied, the level detection comparison operation of the focus error signal can be performed accurately.

  In the present invention, the laser output is set using the relationship between the level change of the laser output and the level change of the focus error signal.

  FIG. 1 is a circuit diagram showing an embodiment of an optical disk recording / reproducing apparatus according to the present invention, FIG. 2 is an explanatory diagram showing the relationship between a photodetector and laser light, and FIG. 3 is used for explaining the operation of the present invention. It is a wave form diagram which shows the focus error signal performed.

  In FIG. 1, reference numeral 1 denotes an objective lens incorporated in an optical pickup, which is supported by a support wire or the like so as to be displaceable in the direction perpendicular to the disk surface and in the radial direction of the disk. Reference numeral 2 denotes a focusing coil for displacing the objective lens 1 in a direction perpendicular to the disk surface. Reference numeral 3 denotes a laser diode that emits laser light. Laser light emitted from the laser diode 3 is collected by the objective lens 1. The disc surface is irradiated by an optical operation.

  A photodetector 4 incorporated in the optical pickup has a function of receiving laser light reflected from the signal surface of the disk and converting it into an electrical signal. The photodetector 4 is composed of A, B, C, and D light receiving sections divided into four as shown in the figure. Reference numeral 5 denotes a first addition circuit for adding signals obtained from the light receiving portions A and C constituting the photodetector 4, and reference numeral 6 denotes a first addition circuit for adding signals obtained from the light receiving portions B and D constituting the photodetector 4. A 2-adder circuit 7 is a subtracter circuit to which signals obtained from the first adder circuit 5 and the second adder circuit 6 are input.

  In such a configuration, the first addition circuit 5, the second addition circuit 6, and the subtraction circuit 7 constitute a focus error signal generation circuit that generates a focus error signal. FIG. 2 shows the relationship between the photodetector 4 and the laser beam reflected from the signal surface of the disk and applied to the photodetector 4, and the irradiation shape changes as shown by the astigmatism. . That is, FIG. 2A shows the in-focus state, and FIGS. 2B and 2C show the state in which the focus is greatly deviated.

  Reference numeral 8 denotes a focus servo circuit to which a tracking error signal output from the subtraction circuit 7 constituting the focus error signal generation circuit is input, and is configured to perform a servo operation for a focus control operation as is well known. Yes. A focus coil drive circuit 9 receives a focus control signal output from the focus servo circuit 8 and supplies a drive signal to the focusing coil 2 in accordance with the control signal. A servo gain setting circuit 10 sets the servo gain of the focus servo circuit 8.

  Reference numeral 11 denotes a laser diode drive circuit that supplies a drive signal to the laser diode 3, and 12 denotes a laser output adjustment circuit that adjusts and sets the level of the drive signal output from the laser diode drive circuit 11. Reference numeral 13 denotes a control circuit for controlling the operation of each circuit, which is constituted by a microcomputer.

  As described above, the optical disk recording / reproducing apparatus according to the present invention is configured. Next, the laser output setting method of the present invention will be described.

  FIG. 3 shows the relationship between the level of the laser output irradiated from the laser diode 3 and the level of the focus error signal. The level of the focus error signal increases as the level of the laser output increases. . That is, in the figure, solid lines A, B, and C indicate changes in the level of the focus error signal when the laser output is changed to the small level P1, the medium level P2, and the large level P3. As is clear from the solid lines A, B and C in the figure, the maximum level on the + side of the focus error signal increases as E1, E2 and E3 as the laser output level increases, and the maximum level on the-side is Like -E1, -E2, and -E3, it becomes larger on the-side.

  The operation for obtaining the relationship between the level of the laser output emitted from the laser diode 3 and the level of the focus error signal is the variable operation of the laser output to the laser output adjustment circuit 12 by the control circuit 13 and the focus coil drive circuit 9. However, the focus servo operation by the focus servo circuit 8 is not performed in such a state where the operation is performed.

  In such a state, a control signal for setting a laser output is output from the control circuit 13 to the laser output adjustment circuit 12. First, a drive signal of a level for irradiating a laser beam of a small level P 1 from the laser diode 3. Is supplied from the laser diode driving circuit 11 to the laser diode 3. In this state, the control operation by the control circuit 13 for the focus coil drive circuit 9 is performed. This operation is, for example, a DC measurement drive whose level continuously changes from the focus coil drive circuit 9 to the focusing coil 2. An operation for outputting a signal is performed.

  The objective lens 1 is displaced in the direction perpendicular to the disk surface by the measurement drive signal supplied from the focus coil drive circuit 9 to the focusing coil 2. The range of the displacement is the maximum on the positive side of the focus error signal level. It is set to change from the value to the maximum value on the negative side.

  When the driving signal for irradiating the laser diode 3 with the laser light of the small level P1 is supplied from the laser diode driving circuit 11 and the driving signal for measurement is supplied from the focus coil driving circuit 9 to the focusing coil 2, As the objective lens 1 is displaced, the level of the tracking error signal output from the subtraction circuit 7 changes. Since the tracking error signal output from the subtracting circuit 7 is input to the control circuit 13, the control circuit 13 converts the input analog signal into a digital signal and measures its level.

  The solid line A shown in FIG. 3 shows the level change of the focus error signal obtained when the laser output is at the small level P1. When the focus error signal level change detection operation is performed when the output of the small level P1 is irradiated from the laser diode 3, the output of the medium level P2 and the large level P3 is irradiated from the laser diode 3. The level change detection operation of the focus error signal can be performed in the same manner. The solid lines B and C in FIG. 3 indicate the level change of the focus error signal obtained when the laser output is at the medium level P2 and the large level P3, respectively.

  As described above, it is possible to detect a change in the level of the focus error signal when the output of the laser light emitted from the laser diode 3 is changed. The relationship between the level of the laser output and the level of the focus error signal. Is stored in a memory circuit (not shown) incorporated in the control circuit 13.

  In this way, the relationship between the laser output level and the focus error signal level can be obtained. On the other hand, the level of the focus error signal suitable for performing the servo operation by the focus servo circuit 8 is set in advance in relation to the focus servo circuit 8, the focus coil drive circuit 9, the focusing coil 2, and the like. Accordingly, the laser diode driving circuit 11 is set so as to supply a driving signal such that the laser output capable of obtaining the focus error signal at the set level is emitted from the laser diode 3. Such a setting operation is performed by controlling the laser output adjustment circuit 12 based on measurement data stored in a memory circuit in the control circuit 13.

  When the setting operation of the laser output irradiated from the laser diode 3 is performed so that a focus error signal at a level suitable for performing the servo operation by the focus servo circuit 8 is obtained, the control circuit for the servo gain setting circuit 10 is next performed. 13 is performed. Such an operation can be performed by irradiating the test disk with a laser output and adjusting the focus servo operation to be performed in an optimum state.

  In this embodiment, the adjustment of the laser output during the recording operation is not described, but many techniques have been developed to make use of the level of laser light reflected from the disk.

It is a circuit diagram which shows one Example of the optical disk recording / reproducing apparatus based on this invention. It is explanatory drawing which shows the relationship between a photodetector and a laser beam. . It is a wave form diagram which shows the focus error signal used in order to demonstrate operation | movement of this invention.

Explanation of symbols

1 Objective lens
2 Focusing coil
3 Laser diode
4 photodetectors
8 Focus servo circuit
9 Focus coil drive circuit 10 Servo gain setting circuit 11 Laser diode drive circuit 12 Laser output adjustment circuit 13 Control circuit

Claims (3)

A focus error signal generated based on a signal obtained from a photodetector incorporated in the optical pickup is input to the focus servo circuit, and a signal output from the focus servo circuit is supplied to the focus coil drive circuit. Is a laser output setting method of an optical disk recording / reproducing apparatus configured to perform a focus control operation by the following: a relationship between the level of a drive signal supplied to a laser diode incorporated in an optical pickup and the level of a focus error signal A laser output setting method for an optical disc recording / reproducing apparatus, characterized in that the level of a drive signal supplied to a laser diode is set so as to emit a laser output from which a focus error signal of a set level is obtained. 2. The laser output setting method according to claim 1, wherein the gain of the focus servo circuit is set after the laser output is set. The relationship between the level of the drive signal supplied to the laser diode and the level of the focus error signal changes in the focusing coil provided to move the objective lens in the direction of the disk surface until the level of the focus error signal is minimized. 2. The laser output setting method according to claim 1, wherein the determination is made by supplying a drive signal.

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