JP2004342279A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the output of a laser beam irradiating the optical disk against the temperature changes in an optical disk drive. <P>SOLUTION: An optical disk drive 1 can stabilize the laser power of a semiconductor laser 60 since the drive can adjust a driving current appropriately even when the temperature of the drive changes. Also, in this optical disk drive 1, a voltage V<SB>T</SB>corresponding to the temperature of the drive is detected by a temperature detecting circuit 10, and the driving current of the semiconductor laser 60 is adjusted in accordance with this voltage V<SB>T</SB>. Consequently, the laser power of the semiconductor laser 60 can be stabilized without introducing the increase of a circuit scale or power consumption. Thus, by stabilizing the laser power of the semiconductor laser 60, the performance of the optical disk drive 1 to read the information from a storage medium can be improved in a wide temperature range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical disk device that reads or writes data by irradiating an optical disk with laser light.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an optical disk device using a DVD-RAM (Digital Versatile Disk Random Access Memory) or the like as a storage medium, a high-frequency current is superimposed on a drive current of a laser beam to be irradiated in order to reduce return light noise. I have.
Return light noise is noise generated when light emitted from a semiconductor laser is reflected on an optical disk as a storage medium and returns to the semiconductor laser.
[0003]
By superimposing a high-frequency current on the drive current of the laser light to be irradiated, it is possible to suppress occurrence of unstable oscillation due to return light, and to prevent occurrence of a reading error or the like.
The return light noise is described in, for example, the reference document “Optical Disc Technology” (written by Radio Engineering Co., Ltd., Morio Onoe, Noboru Murayama, Hiroshi Koide, Kazusaku Yamada, Makoto Kunikane).
Incidentally, the laser power-current characteristic of a semiconductor laser changes with temperature. As the temperature increases, the output laser power decreases even with the same drive current (see FIG. 8).
[0004]
On the other hand, in recent years, the writing or reading speed of an optical disk device has been increasing, and accordingly, writing with a high laser power is required.
Then, the output of the high laser power inevitably raises the temperature of the optical disk device, and thus a situation may occur in which the amplitude of the superimposed high-frequency signal becomes insufficient.
[0005]
As a countermeasure against such a situation, it is conceivable to perform feedback control while monitoring the amplitude of the laser power.
However, since the high-frequency current superimposed on the driving current of the laser beam is about several hundred [MHz], a circuit for monitoring the amplitude of such a high-speed signal becomes large-scale. Then, the heat generation of the monitoring circuit itself causes a problem that the thermal design of the device becomes more difficult, so that such a countermeasure is difficult to realize.
[0006]
Therefore, conventionally, a method of setting the amplitude of a high frequency signal to be superimposed using an external resistor has been used.
FIG. 9 is a circuit configuration diagram of a conventional optical disk device 100 that sets the amplitude of a high frequency signal to be superimposed using an external resistor.
9, the optical disc device 100 includes a reference voltage generation circuit 101, an external resistor 102, a drive bias generation circuit 103, an oscillator 104, a drive circuit 105, and a semiconductor laser 106. In FIG. 9, the optical pickup portion is mainly shown.
[0007]
The reference voltage generation circuit 101 generates a constant voltage (reference voltage V _C ) serving as a reference for generating a bias current input to the semiconductor laser 106, and outputs the generated voltage to the drive bias generation circuit 103.
One end of the external resistor 102 is grounded, and the other end is connected to the drive bias generation circuit 103 via an external resistor connection terminal 103a. The base laser power of the semiconductor laser 106 is determined by the resistance value of the external resistor 102.
[0008]
The drive bias generation circuit 103 drives the semiconductor laser 106 based on the reference voltage input from the reference voltage generation circuit 101 and the resistance of the external resistor 102 connected via the external resistor connection terminal 103a. A current I _{HFM serving} as a base tone is output to the drive circuit 105.
The oscillator 104 generates a high-frequency current signal S _OSC of about several hundred [MHz] (for example, 300 [MHz]) and outputs the signal to the drive circuit 105.
The drive circuit 105 superimposes the current I _HFM input from the drive bias generation circuit 103 and the high-frequency current signal _SOSC input from the oscillator 104, and outputs a drive current for the semiconductor laser 106.
[0009]
The semiconductor laser 106 receives a drive current input from the drive circuit 105, generates a laser beam, and irradiates the optical disc on which data is read or written.
With such a configuration, the laser power of the semiconductor laser 106 can be determined by the resistance value of the external resistor 102.
Further, the resistance value of the external resistor 102 is set to a value such that a sufficient output can be obtained even when the laser power is reduced due to a rise in the temperature of the optical disk device 100.
[0010]
[Non-patent document 1]
Morio Onoe, Noboru Murayama, Hiroshi Koide, Kazusaku Yamada, Makoto Kunikane, "Optical Disc Technology" Radio Technology, p. 40-41
[0011]
[Problems to be solved by the invention]
However, in the method of setting the amplitude of the superimposed high-frequency signal using an external resistor, when the temperature of the optical disc device is low, the amplitude of the laser power becomes excessively large, and it is difficult to control the laser power to a low laser power. The problem that it became.
Also, in the optical disk device, it is often necessary to monitor the temperature of each component at the time of development of the device. However, such a monitoring function is required because of an increase in cost and a limitation of the number of pins due to a mounting area. It was difficult to prepare.
It is an object of the present invention to stabilize the output of a laser beam applied to an optical disk in an optical disk device with respect to a temperature change. In connection with this, it is an object to easily monitor the temperature in the drive circuit of the semiconductor laser.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides
The driving current is obtained by superimposing a high-frequency current signal (for example, a high-frequency current signal S _OSC output from the oscillator 40 in FIG. 1) on a base current (for example, the current I _HFM output from the driving bias generation circuit 30 in FIG. 1). An optical disk device that outputs a laser beam to a laser and reads information from a storage medium (for example, a DVD-RAM or a CD-ROM) or writes information to the storage medium using the laser beam. A temperature detecting means (for example, the temperature detecting circuit 10 in FIG. 1) capable of detecting the temperature change of the laser beam, and the output value of the laser beam is set to an appropriate range in accordance with the temperature change detected by the temperature detecting means. The temperature compensating means (for example, the external resistor 20, the driving bias generating circuit 30, the oscillator 40 and a drive circuit 50).
[0013]
In the optical disk device according to the present invention, the temperature compensating means includes a resistor having a predetermined resistance value (for example, the external resistor 20 in FIG. 1) and a detection result of the temperature detecting means (for example, the temperature in FIG. 1). A drive bias generation circuit (for example, the drive bias generation circuit 30 in FIG. 1) that generates a current that is a basis for the drive current based on the voltage V _T output by the detection circuit 10 and the resistance value of the resistor. An oscillator that generates the high-frequency current signal having a predetermined frequency (for example, the oscillator 40 in FIG. 1), a current generated by the drive bias generation circuit, and a high-frequency current signal generated by the oscillator; A drive circuit (for example, the drive circuit 50 of FIG. 1) that generates the drive current of the laser may be provided.
[0014]
Further, the optical disc device according to the present invention has a configuration in which the resistor can be externally attached to the device, and the terminal for externally attaching the resistor (for example, the external resistor connection terminal 30a in FIG. 1) has the temperature detecting means. May be obtained from outside the device.
That is, with such a configuration, the temperature state inside the optical disk device can be easily monitored from outside the device at the terminal to which the resistor is externally attached.
According to the present invention, an appropriate drive current can be adjusted even when the temperature of the device changes, so that the laser power of the semiconductor laser can be stabilized.
[0015]
In other words, by stabilizing the laser power of the semiconductor laser, it is possible to improve the performance of the optical disk device reading information from or writing information to the storage medium over a wide temperature range.
Further, conventionally, it has been difficult to set a drive current of a semiconductor laser so that a sufficient laser power can be obtained at a high temperature of the device and that the laser power does not become excessively high at a low temperature. Since the drive current on which the high-frequency current signal is superimposed is hardly affected by a change in the temperature of the device, the setting of the drive current during device development becomes easy.
Furthermore, according to the present invention, since the temperature of the device can be monitored via the terminal to which the resistor is externally attached, the thermal design at the time of device development becomes easy.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an optical disk device according to the present invention will be described in detail with reference to the drawings.
First, the configuration will be described.
FIG. 1 is a diagram showing a functional configuration of an optical disc device 1 according to the present embodiment.
In FIG. 1, the optical disc device 1 includes a temperature detection circuit 10, an external resistor 20, a drive bias generation circuit 30, an oscillator 40, a drive circuit 50, and a semiconductor laser 60. In FIG. 1, an optical pickup portion is mainly shown.
Temperature detection circuit 10 is a circuit for generating a voltage V _T corresponding to the temperature.
[0017]
FIG. 2 is a diagram illustrating a circuit configuration example of the temperature detection circuit 10.
2, the temperature detection circuit 10 includes a band gap reference voltage circuit 10a and a voltage generation circuit 10b.
The bandgap reference voltage circuit 10a has the same configuration as a circuit generally used as a reference voltage source, and has a temperature coefficient close to zero, so that it generates a constant voltage (reference voltage V _BG ) regardless of temperature. I do.
[0018]
The voltage generation circuit 10b includes a transistor 11b and a resistor 12b.
The transistor 11b has a gate terminal connected to the output terminal of the differential amplifier circuit of the bandgap reference voltage circuit 10a, and a source terminal to which a current I common to the bandgap reference voltage circuit 10a is input. Further, the drain terminal of the transistor 11b, the resistor 12b is connected, the terminal voltage of the drain terminal becomes the voltage V _T.
[0019]
The resistor 12b is connected to the drain terminal of the transistor 11b, and the current I flows from the transistor 11b.
With this configuration, the voltage generating circuit 10b, by using the fact that current flowing through the transistor 11b I increases in proportion to the temperature, to generate a voltage V _T corresponding to the temperature.
Here, FIG. 3 is a diagram showing a temperature characteristic of the reference voltage V _BG and voltage V _T. In FIG. 3, the reference voltage V _BG has a constant value with respect to a change in temperature, while the voltage _VT has a higher value with temperature.
[0020]
Returning to FIG. 1, one end of the external resistor 20 is grounded, and the other end is connected to the drive bias generation circuit 30 via an external resistor connection terminal 30a. The base laser power of the semiconductor laser 60 is determined by the resistance value of the external resistor 20.
Drive bias generating circuit 30 includes a voltage V _T which is input from the temperature detection circuit 10, based on the resistance value of the external resistor connection terminal 30a external resistor is connected via the 20, drives the semiconductor laser 60 A current I _{HFM serving} as a base tone is output to the drive circuit 50.
FIG. 4 is a diagram illustrating a circuit configuration example of the drive bias generation circuit 30.
[0021]
In FIG. 4, the drive bias generation circuit 30 includes a differential amplifier circuit 31 and transistors 32 and 33.
The differential amplifier circuit 31 has a positive input terminal to which the voltage _VT is input from the temperature detection circuit 10 and a negative terminal connected to the drain terminal of the transistor 32 connected to the output terminal, that is, to the external resistance connection terminal 30a. It is connected.
[0022]
The transistor 32 is a P-type MOS (Metal Oxide Semiconductor), and has a gate terminal connected to the output terminal of the differential amplifier circuit 31 and a source terminal connected to the source terminal of the transistor 33. The drain terminal of the transistor 32 is connected to the negative terminal of the differential amplifier circuit 31 and the external resistor connection terminal 30a.
[0023]
Therefore, transistor 32, when the output of the differential amplifier circuit 31 is ON, the words, in the differential amplifier circuit 31, to conduct when the input voltage at the negative input terminal is not equal to the voltage V _T, the negative input terminal input voltage (external resistor connection terminal 30a) acts to always equal to the voltage V _T.
The transistor 33 is a P-type MOS, and has a gate terminal connected to the output terminal of the differential amplifier circuit 31 and a source terminal connected to the source terminal of the transistor 32. The drain terminal of the transistor 33 is an output terminal of the drive bias generation circuit 30 and outputs a current I _HFM .
[0024]
Here, since the current flowing through the transistor 32 is expressed as V _T / R using the resistance value R of the external resistor 20, the mirror ratio between the transistor 32 and the transistor 33 is 1: N (N is a positive number). ), The current I _HFM is N × V _T / R.
A predetermined bias is applied to the source terminals of the transistors 32 and 33.
[0025]
Returning to FIG. 1, the oscillator 40 generates a high-frequency current signal S _OSC having a predetermined frequency and outputs the signal to the drive circuit 50.
FIG. 5 is a diagram illustrating a circuit configuration example of the oscillator 40.
In FIG. 5, an oscillator 40 includes inverters 41a to 41e and transistors 42a to 42e.
[0026]
The inverters 41a to 41e are current-limited and are connected in a ring to form a ring oscillator.
The oscillation frequency control bias of each of the transistors 42a to 42e is input to the gate terminal. The transistors 42a to 42e supply a clock to each of the inverters 41a to 41e according to the oscillation frequency control bias.
[0027]
Returning to FIG. 1, the drive circuit 50 superimposes the current I _HFM input from the drive bias generation circuit 30 and the high-frequency current signal S _OSC input from the oscillator 40, and outputs a drive current for the semiconductor laser 60.
FIG. 6 is a diagram illustrating a circuit configuration example of the drive circuit 50.
6, the driving circuit 50 includes transistors 51a to 51e and switches 52a and 52b.
[0028]
The transistor 51a is an N-type transistor, and the current input from the drive bias generation circuit 30 is input to a source terminal. Then, the transistor 51a generates the bias voltage VBiasN of the gate terminal by the current I _HFM input to the source terminal.
The transistor 51b forms a pair with the transistor 51a to form a current mirror circuit, and a mirror current corresponding to the current I _HFM flows by the bias voltage VBiasN generated by the transistor 51a.
[0029]
The transistor 51c is a P-type transistor, and the drain terminal is connected to the source terminal of the transistor 51b that forms the current mirror circuit. Then, the transistor 51c generates the bias voltage VBiasP of the gate terminal by the mirror current flowing through the transistor 51b.
The transistor 51d forms a pair with the transistor 51c to form a current mirror circuit, and the current Ip flows from the source terminal to the drain terminal by the bias voltage VBiasP generated by the transistor 51c.
[0030]
The transistor 51e forms a pair with the transistor 51a to form a current mirror circuit, and the current In corresponding to the current I _HFM flows from the source terminal to the drain terminal by the bias voltage VBiasN generated by the transistor 51a.
The switch 52a is provided between the drain terminal of the transistor 51d and the semiconductor laser 60.
[0031]
The switch 52b is provided between the source terminal of the transistor 51e and the semiconductor laser 60.
The switches 52a, 52b receives the high-frequency current signal _{S OSC} input from the oscillator 40 as a clock signal, in response to the amplitude of the high frequency current signal _{S OSC,} switching the ON / OFF. At this time, the switches 52a and 52b switch ON / OFF with opposite polarities in the amplitude of the high-frequency current signal _SOSC .
[0032]
Thus, the semiconductor laser 60, corresponding to the period of the high frequency current signal _{S OSC,} the current Ip output from the transistor 51d by the bias voltage VBIASP, by a bias voltage VBiasN alternately and current In outputted from the transistor 51e Will be entered.
Returning to FIG. 1, the semiconductor laser 60 receives the current Ip and the current In from the drive circuit 50 as a drive current. Then, the semiconductor laser 60 generates a laser beam corresponding to the drive current and irradiates the optical disc on which data is read or written.
[0033]
Next, the operation will be described.
In the optical disk apparatus 1, when reading the information stored in the optical disk, the temperature detection circuit 10 generates a voltage V _T corresponding to the temperature of the device.
The driving bias generation circuit 30 outputs the current _{I HFM} proportional to the voltage _{V T.}
[0034]
Then, the drive circuit 50 superimposes the current I _HFM and the high-frequency current signal S _OSC input from the oscillator 40 and outputs the resultant to the semiconductor laser 60.
As a result, the semiconductor laser 60 outputs a laser having an appropriate laser power corresponding to the temperature of the device.
FIG. 7 is a diagram illustrating a temperature-laser power characteristic of the semiconductor laser 60 of the optical disc device 1. FIG. 7 also shows a temperature-laser power characteristic when the correction corresponding to the temperature of the apparatus is not performed, and a control voltage characteristic for compensating for the fluctuation due to the temperature of the apparatus.
[0035]
As shown in FIG. 7, in the optical disk device 1, even if the temperature of the device changes, the stable laser power is maintained by changing the control voltage so as to cancel the fluctuation due to the temperature.
As described above, the optical disk device 1 to which the present invention is applied can adjust the drive current to an appropriate value even when the temperature of the device changes, so that the laser power of the semiconductor laser 60 can be stabilized.
[0036]
The optical disk apparatus 1 according to the present invention, the temperature detection circuit 10 detects a voltage V _T corresponding to the temperature of the device, on the basis of the voltage V _T, adjusting the drive current of the semiconductor laser 60.
Therefore, the laser power of the semiconductor laser 60 can be stabilized without increasing the circuit scale and the power consumption.
As described above, by stabilizing the laser power of the semiconductor laser 60, the performance of the optical disc device 1 for reading information from a storage medium in a wide temperature range can be improved.
[0037]
Further, conventionally, it has been difficult to set a drive current of a semiconductor laser so that a sufficient laser power can be obtained at a high temperature of the device and that the laser power does not become excessively large at a low temperature. In the optical disk device 1, the drive current on which the high-frequency current signal S _OSC is superimposed is hardly affected by a change in the temperature of the device, so that the drive current can be easily set at the time of device development.
Furthermore, in the optical disk device 1 to which the present invention is applied, the temperature of the device can be monitored via the external resistor connection terminal 30a, so that the thermal design at the time of device development becomes easy.
[0038]
【The invention's effect】
According to the present invention, an appropriate drive current can be adjusted even when the temperature of the device changes, so that the laser power of the semiconductor laser can be stabilized.
That is, by stabilizing the laser power of the semiconductor laser, it is possible to improve the performance of the optical disk device reading information from or writing information to the storage medium over a wide temperature range.
[0039]
Further, conventionally, it has been difficult to set a drive current of a semiconductor laser so that a sufficient laser power can be obtained at a high temperature of the device and that the laser power does not become excessively high at a low temperature. Since the drive current on which the high-frequency current signal is superimposed is hardly affected by a change in the temperature of the device, the setting of the drive current during device development becomes easy.
Furthermore, according to the present invention, since the temperature of the device can be monitored via the terminal to which the resistor is externally attached, the thermal design at the time of device development becomes easy.
[Brief description of the drawings]
FIG. 1 is a diagram showing a functional configuration of an optical disc device 1 according to the present embodiment.
FIG. 2 is a diagram illustrating a circuit configuration example of a temperature detection circuit 10;
3 is a diagram showing temperature characteristics of the reference voltage V _BG and voltage V _T.
FIG. 4 is a diagram illustrating a circuit configuration example of a drive bias generation circuit 30.
FIG. 5 is a diagram showing a circuit configuration example of an oscillator 40.
FIG. 6 is a diagram illustrating a circuit configuration example of a drive circuit 50;
FIG. 7 is a diagram showing a temperature-laser power characteristic of the semiconductor laser 60 of the optical disc device 1;
FIG. 8 is a diagram showing laser power-current characteristics of a semiconductor laser.
FIG. 9 is a circuit configuration diagram of a conventional optical disc apparatus 100 that sets the amplitude of a high frequency signal to be superimposed using an external resistor.
[Explanation of symbols]
1,100 Optical disc device 10 Temperature detection circuit 10a Band gap reference voltage circuit 10b Voltage generation circuit 11b Transistor 12b Resistance 20, 102 External resistance 30, 103 Drive bias generation circuit 30a, 103a External resistance connection terminal 31 Differential amplifier circuit 32 , 33 Transistors 40, 104 Oscillators 41a-41e Inverters 42a-42e Transistors 50, 105 Drive circuits 51a-51e Transistors 52a, 52b Switches 60, 106 Semiconductor laser 101 Reference voltage generation circuit

Claims (3)

An optical disc device that outputs a laser beam to a semiconductor laser by a driving current obtained by superimposing a high-frequency current signal on a base current, and reads information from a storage medium or writes information to the storage medium using the laser light,
Temperature detection means capable of detecting a temperature change in the own device;
In response to the temperature change detected by the temperature detecting means, a temperature compensating means for changing a current serving as a basis of the driving current so that an output value of the laser light is in an appropriate range,
An optical disk device comprising: The temperature compensating means includes:
A resistor having a predetermined resistance value;
A drive bias generation circuit that generates a current that is a basis of the drive current based on a detection result of the temperature detection unit and a resistance value of the resistor;
An oscillator that generates the high-frequency current signal having a predetermined frequency;
A drive circuit that generates the drive current of the semiconductor laser by superimposing a current generated by the drive bias generation circuit and a high-frequency current signal generated by the oscillator;
The optical disk device according to claim 1, further comprising: 3. The optical disk device according to claim 2, wherein the resistance is externally attached to the device, and a detection result of the temperature detecting means can be acquired from outside the device at a terminal to which the resistance is externally attached. .

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