WO2006090740A1

WO2006090740A1 - Light source protecting device and disc device

Info

Publication number: WO2006090740A1
Application number: PCT/JP2006/303173
Authority: WO
Inventors: Kazunori Ishizuka
Original assignee: Pioneer Corporation
Priority date: 2005-02-22
Filing date: 2006-02-22
Publication date: 2006-08-31
Also published as: JPWO2006090740A1; JP4377431B2

Abstract

A light source protecting device (40) is provided to suppress excessive light emission of a laser diode. The light source protecting device (40) includes a temperature sensor (21) and a resistance variable device (30). In a laser diode (20) which is a light source for irradiating a disc with read light or the like, power is supplied from a power supply (Vcc). A temperature sensor (21) detects an ambient temperature, namely, a use temperature, of a laser diode (20). The resistance variable device (30) changes a limit value of a drive current supplied to a laser diode from the power supply (Vcc) based on the ambient temperature of the laser diode (20) measured by the temperature sensor (21).

Description

Specification

Light source protection device and disk device

Technical field

The present invention relates to protection of a light source used for reading an optical disc or the like.

Background art

[0002] In a disk apparatus for reproducing an optical disk or the like and recording / reproducing on an optical disk or the like, a semiconductor laser diode (hereinafter referred to as a laser diode) is used as a light source used for information reading light or information recording light. The laser diode is controlled to generate a constant light output by providing a circuit (APC: Automatic Power Controller) that keeps the light output of the laser diode constant between the power supply and the laser diode. Offer 1). In addition, a current limiting resistor is connected between the power supply and the APC in order to suppress an increase in drive current due to thermal runaway of the laser diode and deterioration of the laser diode due to surge current from the power supply (patented) Reference 1).

[0003] Patent Document 1: Japanese Patent Laid-Open No. 05-95148

Disclosure of the invention

Problems to be solved by the invention

[0004] In order to expand the temperature range in which laser diodes can operate, the drive current at the highest operating temperature (maximum operating temperature) within the range that can guarantee the specified life is set as the limit value of the laser diode drive current. . The resistance value of the current limiting resistor is determined so as to be the limit value of the drive current. For this reason, when the laser diode is used at a temperature lower than the maximum operating temperature (for example, room temperature), the current value of the difference between the limit value and the required drive current value of the laser diode at room temperature is equal to the limit value. Increased more than the current value of the difference from the required drive current value at the maximum operating temperature. That is, the current value of the difference between the limit value and the required drive current value increases as the operating temperature of the laser diode decreases.

[0005] In the case of the laser diode drive circuit disclosed in Patent Document 1, the limit value of the laser diode drive current determined from the resistance value of the current limit resistor is constant. When the operating temperature of a laser diode is low, a driving current exceeding the required driving current value at that operating temperature may flow to the laser diode. In such a case, the laser diode emits excessive light, leading to deterioration of the laser diode.

[0006] Therefore, the present invention solves the above-described problem as an example, and an object thereof is to provide a light source protection device and a disk device that can suppress excessive light emission of a laser diode as a light source.

Means for solving the problem

[0007] The invention according to claim 1 is measured by the temperature detecting means for detecting a use temperature of a light source that emits light when power is supplied from a power source and irradiates the optical disk with light, and is measured by the temperature detecting means. Drive current limit value changing means for changing the limit value of the drive current supplied from the power source to the light source based on the operating temperature of the light source. Brief Description of Drawings

FIG. 1 is a plan view showing a disk device according to this embodiment.

FIG. 2 is a perspective view showing an optical system of a pickup provided in the disk device according to this embodiment.

FIG. 3 is an explanatory diagram showing the relationship between LD drive current and operating temperature.

FIG. 4 is an explanatory view showing a light source protection device according to this embodiment.

FIG. 5 is an explanatory view showing a light source protection device according to a first modification of this embodiment.

FIG. 6 is an explanatory view showing a light source protection device according to a second modification of this embodiment.

FIG. 7 is an explanatory view showing a light source protection device according to a third modification of this embodiment.

FIG. 8 is an explanatory view showing a light source protection device according to a third modification of this embodiment.

FIG. 9 is a circuit diagram showing a circuit for driving a light source according to a conventional example.

Explanation of symbols

[0009] 1 disk device

2 Pickup

2L optical system

20 Laser diode (LD)

21 Temperature sensor 21a thermistor

22 APC

23 Photodiode

30 Variable resistance device

31 1st resistor

32 2nd resistor

33 operational amplifier

34 transistors

35 Microcomputer

40, 40a, 40b, 40c, 40d Light source protection device

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited by the best mode for carrying out the invention (hereinafter referred to as an embodiment). In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

The invention according to this embodiment includes a temperature detection unit that detects a use temperature of a laser diode that irradiates light on an optical disc, and a laser diode based on a use temperature of the laser diode measured by the temperature detection unit. It is characterized in that it includes drive current limit value changing means for changing the limit value of the supplied drive current. In particular, the invention according to this embodiment is suitable for suppressing deterioration due to excessive light emission of the laser diode when the laser diode is used as a light source such as information reading light of an optical disk.

FIG. 1 is a plan view showing a disk device according to this embodiment. This figure shows the disk device viewed from the side opposite to the disk mounting side. FIG. 2 is a perspective view showing an optical system of a pickup provided in the disk device according to this embodiment. The disc device 1 reproduces information recorded on an optical disc (hereinafter referred to as a disc) such as a CD (Compact Disc) or a DVD (Digital Versatile Disc). The disk device according to this embodiment further has a function of recording information on the disk. [0013] The disk device 1 is normally stored in a housing. The disk device 1 includes disk drive means, information reading means for reading information recorded on the disk, and the like. Devices such as a disk driving means, an information reading means, an information reading means support, and an information reading means driving means are attached to the frame 18 provided in the disk device 1.

[0014] The electric motor 8 which is a disk drive means is attached to the frame 18 and rotates the disk. The pickup 2 has an optical system 2L for reading information recorded on the disc. Then, the pickup 2 as information reading means moves in the radial direction of the disc (in the direction of arrow S) while the disc is rotating, and reads the information recorded on the disc. If the disc device 1 has a function of recording information on the disc, the information is recorded on the disc in the process of moving in the radial direction of the disc.

The pickup 2 is supported by a main shaft 3 and a sub shaft 4 that are information reading means supports. The main shaft 3 and the sub shaft 4 are attached to the frame 18. Here, the main axis 3 is an axis that regulates the moving direction and inclination of the pick-up 2. The pickup 2 is formed with a first bearing portion 10 and a second bearing portion 10 which are pickup side support portions, and the main shaft 3 is formed of these.

1 2

It penetrates the part. Further, the pickup 2 is formed with a sub bearing portion 11 that engages with the sub shaft 4. With such a configuration, the pickup 2 includes the first bearing portion 10 and the second bearing portion 10.

1 2 and auxiliary bearing part 11 are supported by main shaft 3 and auxiliary shaft 4 at three points, and move in the radial direction of the disk.

The first bearing portion 10 and the second bearing portion 10 are fitted to and slide on the main shaft 3. For this reason, the first bearing

1 2

A journal bearing is provided in each of the part 10 and the second bearing part 10, and the friction with the main shaft 3 is provided.

1 2

Reduce rubbing. The pickup 2 is moved in the radial direction of the disk by a feed motor 6 which is information reading means driving means. A feed screw 5 is attached to the output shaft of the feed motor 6, and a claw 7 provided on the pickup 2 is aligned with a screw groove formed on the outer periphery of the feed screw 5. As a result, when the feed motor 6 is driven, the pickup 2 moves outward or inward in the radial direction of the disk.

The main shaft 3 and the sub shaft 4 that support the pickup 2 are fixedly supported by the frame body 18. The main shaft 3 is driven by the first fixing screw 9 and the second fixing screw 9 by the first supporting end 3t and the second supporting end 3t force.

1 2 1 2 Attached by being fixed to the frame 18. The main shaft 3 is lubricated with oil. The jar is applied to the inside of the first bearing part 10 and the second bearing part 10.

1 2

Reduces friction with the null bearing.

As shown in FIG. 2, the optical system 2L is stored in an optical system case 2C. The optical system consists of a rising mirror 12, a composite prism 13, a half mirror 14, an objective lens 15, a first condenser lens 16a, a second condenser lens 16b, a light receiving element 17 as a reading means, and a semiconductor laser diode as a light source. (Hereinafter referred to as LD) 20a and 20b. Further, a temperature sensor 21 for measuring the ambient temperature of the LD 20a, 2 Ob is provided in the optical system case 2C.

The laser beams emitted from the two LDs 20 a and 20 b are combined by the combining prism 13 and then reflected by the half mirror 14. Then, after being reflected by the rising mirror 12 through the first condenser lens 16a, it is condensed by the objective lens 15 arranged at a position facing the rising mirror 12, and irradiated onto the recording surface of the disk. This laser beam is reflected on the recording surface of the disk, and is guided to the light receiving element 17 through the objective lens 15, the rising mirror 12, the first condenser lens 16a, the half mirror 14, and the second condenser lens 16b. In the following description, LD20a and LD20b are referred to as LD20 without particular distinction.

FIG. 3 is an explanatory diagram showing the relationship between the LD drive current and the operating temperature. FIG. 9 is a circuit diagram showing a circuit for driving a light source according to a conventional example. Since the loss current increases as the operating temperature Ta rises in the LD used as the light source for the optical system provided in the disk device pickup, the current value required to drive the LD (hereinafter referred to as the required drive current value) Iopd is It increases as the operating temperature Ta of the LD increases (see Fig. 3). Here, the operating temperature Ta of the LD means the temperature of the LD when the LD is operating.

[0021] LD degrades as the use temperature Ta increases. On the other hand, since LD wants to make the operable temperature range as large as possible, set the highest operating temperature (maximum operating temperature) Tal within the range that can guarantee the specified life. When the operating temperature of the LD exceeds the maximum operating temperature Tal, control for executing the protection operation (for example, operation stop) of the LD is generally performed. Therefore, the drive current exceeding the required drive current value at the maximum operating temperature Tal is not applied to the LD.

[0022] Here, since the actual LD has manufacturing variations and operation variations, for example, as shown in FIG. 9, in a conventional circuit for driving a light source, a required drive current at the maximum operating temperature Tal is required. The current value obtained by adding the margin current value Im considering the manufacturing variation of the LD120 to the value was set as the maximum drive current value II of the LD120. That is, no current exceeding the maximum drive current value II is applied to the LD 120 in the operating temperature range of the LD 120 (maximum operating temperature Tal or less).

However, such a setting may cause problems when the LD 120 is driven at the maximum operating temperature Tal or lower. For example, when the LD120 is driven at the operating temperature Tal (Tal <Ta), the required drive current value of the LD120 is lopl (Fig. 3). At this time, as shown in Fig. 3.

1

Furthermore, since the maximum drive current value of LD120 is II, excess current exceeding the required drive current value lopl may be applied to LD120 at operating temperature Tal. For example, as shown in Figure 9.

1

LD120 is necessary when the optical output control function of the APC122 stops working due to poor soldering of the APC122 (hereinafter referred to as APC: Automatic Power Controller) 122 or malfunction due to the deterioration of the APC122 itself. Excessive drive current value exceeding lopl

1

Current may be applied. In such a case, the LD 120 emits excessive light, leading to deterioration of the LD 120.

FIG. 4 is an explanatory view showing the light source protection device according to this embodiment. The light source protection device 40 according to this embodiment suppresses the deterioration of the LD due to the excessive light emission of the LD, and the limit value of the drive current lop of the LD 20 (hereinafter referred to as the drive current limit value) according to the operating temperature Ta of the LD. Change lopl. Here, the drive current of the LD 20 is a current applied from the power source Vcc to the LD 20 in order to drive the LD 20.

In this embodiment, as shown in FIG. 4, a light source protection device 40 is provided between the power source Vcc of the LD 20 and the APC 22 which is a constant optical output control unit, and according to the operating temperature Ta of the LD 20. Then, the drive current limit value lopl is changed. Specifically, as shown by the solid line in FIG. 3, the drive current limit value lopl is increased as the operating temperature Ta of the LD 20 increases.

However, the drive current limit value lopl is set so as not to exceed the maximum drive current value II of the LD20 determined based on the maximum use temperature Tal of the LD20. That is, the drive current limit value lopl is not more than the maximum drive current value II. As a result, it is possible to prevent the excessive drive current lop from being applied to the LD 20 and to reliably operate the LD 20 up to the maximum operating temperature Tal of the LD 20. Next, the configuration of the light source protection device 40 according to this embodiment explain.

[0027] The light source protection device 40 according to this embodiment includes a temperature sensor 21 as a temperature detecting means for detecting the ambient temperature of the LD 20 that is a light source, and the LD 20 based on the ambient temperature of the LD 20 measured by the temperature sensor 21. And the resistance variable device 30 as a drive current limit value changing means for changing the drive current limit value lopl of the. In this embodiment, the operating temperature Ta of the LD20 is represented by the ambient temperature of the LD20.

In this embodiment, the light source protection device 40 is provided between the power source Vcc of the LD 20 and the APC 22. Here, the light source protection device 40 may be provided between the APC 22 and the LD 20. However, in this case, an excessive current may flow to APC22 when a surge is applied. By providing the light source protection device 40 between the power source Vcc of the LD 20 and the APC 22 as in this embodiment, an excessive current flowing to the APC 22 by the light source protection device 40 can be suppressed.

The resistance variable device 30 is connected in series between the power source Vcc of the LD 20 and the APC 22. The LD 20 is connected to the APC 22 in series and is driven by the APC 22. In the vicinity of the LD 20, a photodiode 23 is provided as a light detection means for detecting the light amount of the LD 20. The APC 22 acquires the terminal voltage of the photodiode 23 and calculates the light emission amount of the LD 20 based on the change. Based on the calculation result, the APC 22 controls the LD driving current lop so that the LD 20 emits light with a constant output. As a result, the LD 20 emits light with a constant output.

The variable resistance device 30 included in the light source protection device 40 changes the resistance value based on the ambient temperature of the LD 20 detected by the temperature sensor 21 so that the drive current limit value lopl of the LD 20 is indicated by a solid line in FIG. Change to As a result, even if the optical output control function of the APC22 does not work, the LD drive current lop applied to the LD20 does not exceed the drive current limit value lopl of the LD20. As a result, excessive light emission of LD20 can be suppressed and deterioration of LD20 can be suppressed.

As the temperature sensor 21, for example, a temperature detection element such as a thermocouple or thermistor can be used. The variable resistance device 30 can be a so-called variable resistor, for example. Then, based on the ambient temperature of the LD 20 detected by the temperature sensor 21, the variable resistor may be controlled by an actuator. In addition, variable resistance device 3 0 is an electronic variable resistor using a so-called IC (Integrated Circuit), and does not convert the electrical signal of the temperature sensor 21 force into a mechanical motion. 30 may be controlled.

Here, the drive current limit value Iopl of the LD may be the required drive current value Iopd of the LD, but in this embodiment, the margin current value Im is added to the required drive current value Iopd of the LD. Value (Iopd + Im). This is because the required drive current value Iopd required to obtain the same optical output varies due to variations in the operation and manufacturing of the LD. This is to allow the LD to emit light.

[0033] Further, the drive current limit value Iopl of the LD may be set according to the LD having the smallest necessary drive current value Iopd necessary for obtaining the same optical output. In this way, there is less risk of excessive current being applied to an LD with a small required drive current value Iopd required to obtain the same light output. As a result, it is possible to more reliably suppress the degradation of the LD when there is a manufacturing variation or driving variation of the LD. The LD drive current limit value Iopl can be set by selecting an appropriate setting method from the above setting methods according to the specifications of the disk device 1 and the like.

[Modification 1]

FIG. 5 is an explanatory view showing a light source protection device according to a first modification of this embodiment. This light source protection device uses a thermistor as the temperature detection means, and changes the input voltage input to the op amp used as the drive current limit value changing means based on the change in the resistance value of the thermistor due to the change in the ambient temperature of the LD. As a result, the LD drive current limit value Iopl is changed.

The light source protection device 40a includes a thermistor 21a that is a temperature detection means and an operational amplifier 33 that is a drive current limit value changing means, and further includes a first resistor 31, a second resistor 32, and an LD drive current. A transistor 34 as a control element is provided. The light source protection device 40a according to this modification is provided between the power supply Vcc and the APC22. The first resistor 31 is connected between the power supply Vcc and the emitter of the transistor 34. The collector of transistor 34 is connected to APC22. [0036] The current flowing from the power source Vcc branches to the second resistor 32 at the branch point A and flows to the thermistor 21a connected in series therewith. The current flowing through the second resistor 32 branches at a branch point B, one of which is input to the thermistor 21 a and one of which is input to the operational amplifier 33. The output of the first resistor 31 branched at the branch point C is input to the operational amplifier 33. The output of the operational amplifier 33 is input to the base of the transistor 34. As a result, the input to the base of the transistor 34 can be controlled by the output of the operational amplifier 33, and the magnitude of the current It flowing to the APC 22 can be controlled.

[0037] In the light source protection device 40a according to this embodiment, when the voltage between the branch point Α and the branch point Β is V and the resistance value of the first resistor 31 is R, the current flows between the emitter and collector of the transistor 34.

twenty one

Thus, the current It flowing through the APC 22 can be obtained by equation (1).

It = V / R (1)

twenty one

[0038] The resistance value R of the thermistor 21a decreases as the temperature rises. By thermistor 21a

t

As the ambient temperature of the detected LD20 increases, the resistance value R of the thermistor 21a decreases.

t

Thus, the voltage V between the branch point B and ground becomes small. Voltage between branch point A and ground is 1 t

Therefore, when V becomes smaller, the voltage V between branch point A and branch point B increases. Do

t 2

From equation (1), It increases.

[0039] The current It determined by the equation (1) is a current output from the light source protection device 40a according to this modification and input to the APC 22. This current changes as shown by the solid line in FIG. 3 as the ambient temperature of the LD 20, that is, the operating temperature Ta of the LD 20 increases. Therefore, if It is assumed that the LD drive current limit value Iopl is increased, the drive current limit value Iopl of LD20 can be increased as the operating temperature Ta of the LD20 increases.

[0040] According to this, even if the optical output control function of APC22 stops working, the LD drive current lop applied to the LD20 does not exceed the drive current limit value Iopl of the LD20. . As a result, excessive light emission of the LD20 can be suppressed and deterioration of the LD20 can be suppressed.

[0041] (Modification 2)

FIG. 6 is an explanatory view showing a light source protection device according to a second modification of this embodiment. The light source protection device 40b has substantially the same configuration as the light source protection device 40a according to the first modification. However, the base of the transistor 34 is connected to the branch point B through the third resistor 33. Even with such a configuration, the input to the base of the transistor 34 can be changed based on the change in the resistance value of the thermistor 21a. As shown by the solid line in FIG. 3, the driving force limit value lopl of the LD 20 can be increased as the operating temperature Ta of the LD 20 increases.

[0042] Accordingly, even if the optical output control function of the APC22 stops working, the LD drive current lop applied to the LD20 does not exceed the drive current limit value lopl of the LD20. . As a result, excessive light emission of the LD20 can be suppressed and deterioration of the LD20 can be suppressed.

[0043] (Modification 3)

7 and 8 are explanatory views showing a light source protection device according to a third modification of this embodiment. The light source protection device 40c shown in FIG. 7 directly obtains the temperature of the thermistor 21a by the force microcomputer 35 having substantially the same configuration as the light source protection device 40a according to the first modification of this embodiment, and converts the temperature into voltage. The difference is that it is input to operational amplifier 33. The light source protection device 40d shown in FIG. 8 directly obtains the temperature of the thermistor 21a by the force microcomputer 35 having substantially the same configuration as the light source protection device 40b according to the second modification of this embodiment, and uses the temperature as a voltage. The difference is that it is converted and input to operational amplifier 33. This microcomputer 35 is advantageous in that it is not necessary to newly provide a circuit for temperature detection because the disk device 1 can use a microcomputer provided for controlling the operation of the LD 20 and the like. is there.

[0044] In the first to third modifications of this embodiment, the ambient temperature of the LD is detected by a thermistor. For example, the ambient temperature of the LD is detected by a thermocouple, and the thermoelectric power is detected. The transistor 34 (FIGS. 5, 6, etc.) that is the LD drive current control element may be controlled by controlling the LD drive current control value lopl.

As described above, the light source protection device according to this embodiment and the modification thereof is a temperature detection unit that detects the ambient temperature of the light source (LD) that emits light when power is supplied from the power source and irradiates the optical disk with light. Temperature sensor, thermistor, etc.) and the control of the drive current supplied from the power source to the light source based on the ambient temperature of the light source measured by the temperature detecting means. Drive current limit value changing means (resistance variable device, operational amplifier, etc.) for changing the limit value (drive current limit value Iopl). As a result, even if the optical output control function of the APC does not work, the drive current lop applied to the LD does not exceed the LD drive current limit value Iopl. As a result, excessive light emission of the LD can be suppressed and deterioration of the LD can be suppressed.

Industrial applicability

As described above, the light source protection device and the disk device according to the present invention are useful for protecting a light source used in an optical disk device or the like, and are particularly suitable for suppressing excessive light emission of the light source.

Claims

The scope of the claims

[1] Temperature detecting means for detecting the operating temperature of a light source that emits light when power is supplied from a power source, and irradiates the optical disk with light;

A drive current limit value changing means for changing a limit value of the drive current supplied from the power source to the light source based on the operating temperature of the light source measured by the temperature detecting means;

A light source protection device comprising:

[2] The light source protection device according to claim 1, wherein the limit value of the drive current is equal to or less than a maximum drive current value of the light source, which is determined based on a maximum operating temperature of the light source. .

[3] The light source protection device according to claim 1 or 2,

A light source protection device, which is provided between the power source and a light output constant control means for controlling the light output of the light source to be constant.

[4] The temperature detecting means is an element whose resistance value changes with temperature,

The drive current limit value changing means changes the limit value of the drive current supplied to the light source based on a change in the resistance value of the element. Or the light source protection device according to item 1.

[5] disk drive means for rotating the disk;

A light source for irradiating the disc with light;

Claims:! To 4 of the light source protection device according to any one of

A disk device comprising: