JP2008293607A - Optical pickup unit and optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise recording specifications on an optical disk drive by utilizing laser output capabilities of each optical pickup unit (OPU). <P>SOLUTION: An OPU 10 is equipped with a storage section 7 which stores a value of light use efficiency k in relation to an optical system 2 which transmits a laser beam emitted from a laser diode (LD) 1 to an objective lens 4. A control circuit 14 of the optical disk drive 20 sets the recording specifications of a loaded optical disk 11 based on the light use efficiency k read from OPU 10. The value of the light use efficiency k is computed as k=α2/α1 which is a ratio of a tilt α1 of I-L characteristics for a single LD against a tilt α2 of I-L characteristics when including the LD in the OPU and producing output from the objective lens. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical pickup unit and an optical disc apparatus for efficiently recording data on a recordable optical disc.

  In a conventional optical disk apparatus (drive apparatus), an upper limit value of recording power used in the apparatus is set based on a laser output specification value of an optical pickup unit (hereinafter referred to as OPU), and an operation specification of the apparatus is determined. For example, since high output power is required for high-speed recording, a drive device equipped with a low-output specification OPU does not include operation specifications in the high-speed mode. If the OPU or device is operated under conditions exceeding those specifications, the life of the OPC laser light source will be shortened and the quality of data recorded on the optical disk will be impaired.

  In Patent Document 1, in order to prevent damage (recording failure) to an optical disk due to deterioration of laser output, the degree of instability of laser output is recorded in storage means, and laser output and storage at the time of trial writing (during OPC). Disclosed is to determine whether or not recording is possible on an optical disc by comparing the instability of the laser output recorded in the means.

JP 2005-327438 A

  Conventional optical output specifications of the OPU are uniformly determined according to the lower limit value of the distribution in consideration of the average value of the distribution or the safety side when the output value of each OPU is distributed. In the case of this method, there is no particular problem if the output performance of the OPU has a margin with respect to the required specifications on the apparatus side.

  However, when using an OPU of blue-violet laser light such as Blu-Ray Disc (BD), the operation margin is reduced, which is a problem. The reason is that the blue-violet laser for BD has a lower output power than the laser for CD and DVD, so that the emitted laser light is greatly affected by the variation of the far field image (FFP) and reaches the disk surface. This is because the effective optical power may be insufficient. As a result, the operation specifications of the apparatus must be set to those with uniform performance. In such a conventional method, since the output performance of each OPU is not taken into consideration, the capability cannot be fully utilized even though the device is individually equipped with a high-performance OPU. In other words, high-speed recording performance that was technically possible has not been put into practical use as a specification of the apparatus.

  In view of the above problems, an object of the present invention is to improve recording specifications set in an optical disc apparatus by utilizing the laser output capability of each OPU.

  The optical pickup unit of the present invention includes a laser diode that emits laser light, an optical system that collects the emitted laser light and transmits it to an objective lens facing the optical disc, and a light receiving device that receives the laser light and converts it into an electrical signal. A laser diode driver that drives the laser diode, and a storage unit that stores a value of light utilization efficiency of the optical system.

  Here, the value of the light utilization efficiency is the slope α1 of the current versus light output characteristic (hereinafter referred to as IL characteristic) in the state of the laser diode alone, and the state in which the laser diode is incorporated into the optical pickup unit and output from the objective lens. It is calculated as a ratio of the slope of the IL characteristic to α2, k = α2 / α1.

  An optical disk apparatus according to the present invention includes a spindle motor that rotates a mounted optical disk, an optical pickup unit that irradiates a laser beam on the optical disk, and holds a value of light utilization efficiency of a built-in optical system, a spindle motor, A control circuit for controlling the optical pickup unit, and the control circuit sets a recording specification for the mounted optical disk based on the light utilization efficiency read from the optical pickup unit.

  According to the present invention, even when the output margin of the OPU is small like a BD disc, there is an effect of improving the recording specification of the optical disc apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of an optical pickup unit (OPU) according to the present invention. The optical pickup unit 10 includes a laser diode (LD) 1 that is a light emitting element, an optical system 2 that transmits the laser light to the disk surface, a laser diode driver (LDD) 5 that drives the LD 1, and an optical signal that receives the laser light. The light-receiving part 6 to convert and the memory | storage part (EEPROM) 7 which memorize | stores the performance of OPU10 are provided. The optical system 2 includes a collimator lens, a polarizing beam splitter, an actuator 3, an objective lens 4, and the like. In the EEPROM 7, light transmission efficiency (hereinafter referred to as light utilization efficiency) in the optical system 2 is written and held. The OPU performance measuring device 9 is a device that measures the light utilization efficiency of each OPU. For example, the manufacturer of the OPU measures the light utilization efficiency using the measuring device 9 for each manufactured OPC and writes it in the EEPROM 7. Note that the performance (maximum output power) of the LD 1 may be further written in the EEPROM 7.

  FIG. 2 is a block diagram showing an embodiment of an optical disc apparatus according to the present invention. The optical disk device (drive device) 20 is mounted with the optical pickup unit (OPU) 10 shown in FIG. 1, and also receives signals from the spindle motor 12 that rotates the mounted optical disk 11 and the light receiving unit 6 in the OPU. And an arithmetic circuit 13 for generating a focus error signal and a tracking error signal, and a control circuit 14 for controlling the spindle motor 12, the actuator 3, and the LDD 5. The control circuit 14 receives the focus error signal / tracking error signal from the arithmetic circuit 13 and sends a focus / tracking control signal to the actuator 3. Further, a recording specification for the loaded disk 11 is set based on the OPU performance information (light utilization efficiency) read from the EEPROM 7, the output laser power is limited to the LDD 5 and the speed of the spindle motor 12 is limited. At that time, since the specifications are determined based on the performance information of the installed OPU 10, the laser output capability of each OPU 10 can be utilized to the maximum.

  FIG. 3 is a diagram for explaining how to obtain the light use efficiency of the optical pickup unit (OPU). For this purpose, the optical output characteristics of the laser diode (LD) 1 and the OPU 10 (the relationship between current and optical output, hereinafter referred to as IL characteristics) are measured using the light utilization efficiency measuring device 9 and the optical transmission efficiency of the OPU 10 is calculated. To do.

  First, the IL characteristic in a single LD state is measured in advance, and the slope of the IL characteristic at this time is α1. Next, an IL characteristic in a state where the LD is incorporated as an OPU, that is, an output from the objective lens 4 of the OPU is measured. The slope of the IL characteristic at this time is α2. Then, the transmission efficiency of the optical system 2, that is, the light use efficiency k of the OPU 10 is determined by calculating the ratio k = α2 / α1 between the two slopes. This light utilization efficiency k has a different value for each OPU due to the spot shape (FFP) of the LD emitted light and the assembly accuracy of the optical system 2.

FIG. 4 is a diagram showing an example of setting the recording specifications of the optical disc apparatus.
Here, it is assumed that data is recorded on two types of discs A and B. The recording power required for the disc A is 10 mW at 2 × speed and 15 mW at 4 × speed. The recording power required for the disc B is 13 mW at double speed and 18 mW at quad speed. These values can be obtained by performing test writing (OPC) on the loaded disc. Alternatively, a recommended value determined for each medium may be used.

  On the other hand, it is assumed that two types of OPUs (# 1, # 2) are installed in the drive device. As for the performance of the OPU, the light emission power (maximum rated value) Ps of the single LD is 100 mW, the light use efficiency k is 15% for OPU (# 1), and 20% for OPU (# 2). The light utilization efficiency k is held in the EEPROM in each OPU. Although the rated value may be used as it is for the light emission power Ps of the single LD, if the maximum permissible value is measured separately for each OPU, the accuracy becomes higher by using that value.

  In the case of OPU (# 1), the maximum output power Pm emitted from the objective lens of the OPU is 100 × 15% = 15 mW. In the case of OPU (# 2), the maximum output power Pm is 100 × 20% = 20 mW. The maximum output power Pm and the recording power required for the disks A and B are compared to determine the upper limit speed at which recording is possible within the range of the maximum output power Pm. As a result, when the disk A is recorded by a device equipped with OPU (# 1), the upper limit is 4 × speed. However, when recording the disk B with this apparatus, the upper limit is double speed. In the case of an apparatus equipped with OPU (# 2), the upper limit is 4 × speed for both of disk A and disk B.

  In this way, the recording specification (upper speed) of the drive device is set so that recording can be performed at the highest possible speed according to the capability of the installed OPU. In other words, since the maximum light emission power of the LD built in the OPU is individually controlled within an allowable range, there is no possibility of being destroyed or shortened by an overload.

FIG. 5 is a diagram illustrating an example of a flowchart for obtaining and storing light utilization efficiency in the optical pickup unit (OPU).
In S101, the IL characteristic is measured in advance in the state of the LD1 alone, and the inclination α1 is obtained. In S102, the OPU 10 is assembled using the measured LD and optical system. In S103, the IL characteristic is measured in the OPU state, and the slope α2 is obtained. In S104, a ratio k = α2 / α1 between the two slopes is calculated to obtain the OPU light utilization efficiency k. In S <b> 105, the calculated value of light utilization efficiency k is written in the EEPROM 7.

FIG. 6 is a diagram showing an example of a flowchart for setting recording specifications in the optical disc apparatus.
In S201, the disc management information is read from the loaded disc. This describes the recording conditions (recording power and maximum recording speed) of the disc. Alternatively, the recording condition for the disk ID stored in advance in the memory of the apparatus may be searched from the disk ID.

  In S202, the light utilization efficiency k is read from the EEPROM 7 of the OPU. In S203, the maximum output power Pm is calculated from the light emission power Ps of the LD built into the OPU and the read light utilization efficiency k.

  In S204, the disk is rotated at the maximum recording speed (for example, quadruple speed) described on the disk. In S205, trial writing (OPC) is performed on the disk, and the optimum recording power Popt at that speed is obtained. In S206, it is determined whether or not the obtained optimum recording power Popt is equal to or less than the maximum output power Pm of the OPU. If Popt ≦ Pm, the process proceeds to S208, and the speed (4 × speed) is set to the recording specification (upper speed).

  If Pop> Pm is determined in S206, the process proceeds to S207, and the recording speed is lowered. For example, the speed is reduced from 4 × to 2 ×. Then, returning to S205, OPC is performed again at the double speed to obtain the optimum recording power Popt. In this manner, the maximum recording speed Vm that satisfies Popt ≦ Pm is obtained in S206, and Vmax and Popt are set to recording specifications (upper limit values) in S208.

  As described above, according to the present embodiment, it is possible to perform recording at the highest possible speed according to the capability of the installed OPU. Therefore, even when the output margin of the OPU is small like a BD disc, there is an effect of improving the recording specifications of the optical disc apparatus.

The block diagram which shows one Example of the optical pick-up unit (OPU) concerning this invention. The block diagram which shows one Example of the optical disk apparatus concerning this invention. The figure explaining how to obtain | require the optical utilization efficiency of OPU. The figure which shows an example of the setting of the recording specification of an optical disk device. The flowchart which calculates | requires and stores light utilization efficiency in OPU. 6 is a flowchart for setting recording specifications in an optical disc apparatus.

Explanation of symbols

1 ... Laser diode (LD)
2 ... Optical system 5 ... Laser diode driver (LDD)
6 ... light receiving unit 7 ... storage unit (EEPROM)
DESCRIPTION OF SYMBOLS 3 ... Actuator 4 ... Objective lens 9 ... OPU performance measuring apparatus 10 ... Optical pick-up unit (OPU)
DESCRIPTION OF SYMBOLS 11 ... Optical disk 12 ... Spindle motor 13 ... Arithmetic circuit 14 ... Control circuit 20 ... Optical disk apparatus (drive apparatus).

Claims (5)

In an optical pickup unit for recording data by irradiating an optical disc with laser light,
A laser diode that emits laser light;
An optical system that collects the emitted laser light and transmits it to an objective lens facing the optical disc;
A light receiving unit that receives laser light and converts it into an electrical signal;
A laser diode driver for driving the laser diode;
An optical pickup unit comprising: a storage unit that stores a value of light utilization efficiency of the optical system. The optical pickup unit according to claim 1,
The value of the light use efficiency is output from the objective lens when the laser diode is incorporated into the optical pickup unit, the slope α1 of the current versus light output characteristic (hereinafter referred to as IL characteristic) in the state of the laser diode alone. An optical pickup unit, which is calculated as a ratio of the IL characteristic slope α2 in a state, k = α2 / α1. In an optical disc apparatus for recording data on an optical disc,
A spindle motor that rotates the mounted optical disk;
An optical pickup unit that irradiates the optical disc with laser light and holds the value of the light utilization efficiency of the built-in optical system;
A control circuit for controlling the spindle motor and the optical pickup unit;
The control circuit sets a recording specification for the mounted optical disk based on the light utilization efficiency read from the optical pickup unit. The optical disk apparatus according to claim 3,
The optical disc apparatus, wherein the control circuit sets an upper limit value of a recording speed for the optical disc within a range of a maximum output of laser light determined from light use efficiency of the optical pickup unit. The optical disk apparatus according to claim 4, wherein
The control circuit obtains an optimum recording power by performing trial writing on the optical disc at a predetermined recording speed, and sets an upper limit value of the recording speed in comparison with a maximum output of the optical pickup unit. Optical disk device.

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