JP2006048885A - Laser driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser driving device that can support higher speed. <P>SOLUTION: The laser driving device drives a semiconductor laser 3 to emit light in a pulse-like manner in accordance with a digital signal and is provided with a temperature sensor 5, a recording pulse generator 1, an auxiliary pulse generator 4, and an adder 8. The temperature sensor 5 produces a measured temperature that changes in accordance with a temperature of the semiconductor laser. The recording pulse generator 1, the auxiliary pulse generator 4, and the adder 8 output a pulse-like signal having a shape corresponding to the measured temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser driving device used for recording digital information on a phase change recording type optical disk such as a DVD in an optical disk recorder or an optical disk drive for a PC.

  In recent years, demand for rewritable optical disk devices has increased in the fields of computer auxiliary storage devices and consumer video recorders. In order to form a recording mark on an optical disc, a semiconductor laser light source is generally used. In order to form a good recording mark, the semiconductor laser needs to emit light in pulses. In order to generate an optical pulse, a laser driving device that adds a pulse current and supplies it to a semiconductor laser is conventionally used.

  In general, as shown in FIG. 31, a laser driving apparatus has a multi-pulse generating unit as a main part, and an input digital information signal (NRZ signal) is converted into a writing signal composed of a pulse group, and is passed through a current driving amplifier. Is supplied to the semiconductor laser, and information is recorded or erased on the phase change recording type optical disc. When the crystallized phase change optical disk is irradiated with a semiconductor laser, rapidly heated, and then rapidly cooled, an amorphous mark is formed. Depending on the contents of the digital information, information “1” may be continuously recorded. At this time, if the semiconductor laser of constant power is irradiated uniformly, the central portion of the mark is excessively heated due to heat accumulation, and as a result, the shape of the formed mark may be distorted. Therefore, conventionally, when recording continuous information, so-called multi-pulse recording in which a semiconductor laser emits light intermittently has been performed.

  However, the demand for speeding up of the optical disc apparatus has been increasing year by year. When the clock rate of the recording pulse is increased to cope with this, individual pulses constituting the multi-pulse cannot be emitted correctly. That is, in the process of supplying a current from the laser driving device to the semiconductor laser, it is more greatly affected by a load such as a series resistor, a capacitor or an inductor, or a wiring capacitance that is equivalently built in the semiconductor laser. As a result, the pulse waveform, which should be rectangular in nature, becomes dull in a triangular shape.

Therefore, conventionally, a kind of waveform equalization is performed on each pulse (see, for example, Patent Document 1). That is, a current having a waveform such that the leading portion of each pulse is stronger than the other portions is supplied to the semiconductor laser to compensate for the waveform blunting caused by the load.
JP 2002-298349 A

However, it has been found by the inventor's investigation that in the conventional configuration, an excessive or insufficient compensation occurs when trying to cope with higher speeds.
In particular, in recent years, a blue-violet laser having an oscillation wavelength of 400 nm is often used as a semiconductor laser, and in this case, the data transfer rate during standard speed recording is set to 36 Mbps. As the speed increases further in the future, the rise time of the optical pulse waveform needs to be 1.5 ns or less in order for the optical pulse waveform to reach the peak level during pulse modulation of the semiconductor laser.

However, the blue-violet laser has a structure whose series resistance value is often more than three times that of the red laser, is greatly affected by the low-pass filter formed together with the capacitive load of the drive circuit, and is difficult to perform high-speed modulation.
Therefore, an object of the present invention is to provide a laser driving device that can cope with higher speed.

According to the investigation of the present inventor, the excess or deficiency of the compensation in the conventional configuration is caused by the load fluctuation due to the temperature fluctuation, in other words, this is one factor that cannot increase the temperature margin of the system. ,There was found.
Therefore, the present invention provides a laser driving apparatus that can always perform optimum pulsed light emission even when the load fluctuates due to a temperature change by the following means.

  According to a first aspect of the present invention, there is provided a laser driving device that emits a semiconductor laser in a pulsed manner in response to a digital signal, and includes a measuring unit and a pulse generating unit. The measuring means outputs a measured value that changes according to the temperature of the semiconductor laser. The pulse generating means outputs a pulse signal having a shape corresponding to the measured value.

  Here, the digital signal is, for example, a recording signal recorded on an optical disk or the like using a semiconductor laser. The measured value that changes according to the temperature of the semiconductor laser is, for example, a value that directly or indirectly indicates the temperature of the semiconductor laser. The measured value of the semiconductor laser or the characteristic value of the semiconductor laser It is a measured value, more specifically, an electrical characteristic value such as a voltage value, a current value, and a resistance value. The pulse signal is output to the semiconductor laser as a pulse current, for example.

With the laser driving device of the present invention, even when the load fluctuates due to temperature fluctuations of the semiconductor laser, it is possible to appropriately perform pulsed light emission.
A laser driving device according to a second aspect is the laser driving device according to the first aspect, wherein the measuring means is a device for measuring the temperature of the semiconductor laser.

A laser driving device according to a third aspect is the laser driving device according to the first aspect, wherein the measuring means is a device for measuring a voltage value or a resistance value of the semiconductor laser.
The laser drive device according to claim 4 is the laser drive device according to any one of claims 1 to 3, wherein the pulse generation means includes a first pulse generation unit, a second pulse generation unit, And an adder. The first pulse generator generates a first pulse signal having a constant peak value. The second pulse generation unit generates a second pulse signal whose peak value changes according to the measurement value. The adder adds the first pulse signal and the second pulse signal and outputs a pulse signal.

With the laser driving device of the present invention, for example, it is possible to compensate the first pulse signal corresponding to the digital signal with the second pulse signal corresponding to the measured value and output the pulse signal.
The laser drive device according to claim 5 is the laser drive device according to claim 4, wherein the second pulse generation unit includes a third pulse generation unit and a fourth pulse generation unit. ing. The third pulse generator generates a third pulse signal which is a forward signal with respect to the first pulse signal and whose peak value changes according to the measured value. The fourth pulse generation unit generates a fourth pulse signal that is a signal in the opposite direction to the first pulse signal, and whose peak value changes according to the measurement value.

The third pulse signal and the fourth pulse signal are output as a second pulse signal and added by an adder.
With the laser drive device of the present invention, for example, not only forward compensation but also backward compensation can be performed on the first pulse signal. For this reason, it becomes possible to output a pulse signal having a more appropriate pulse shape.

  A laser driving device according to a sixth aspect is the laser driving device according to the fourth or fifth aspect, wherein the measuring means is a device for measuring the temperature of the semiconductor laser. The second pulse generation unit further includes a correction peak value determining unit that determines the peak value of the second pulse signal in a monotonically decreasing relationship according to the measurement value.

  In the laser driving device of the present invention, even if the load varies depending on the temperature, the peak value of the second pulse signal can be uniquely changed according to the temperature. In addition, it becomes possible to control the peak value so that the peak value becomes higher as the temperature is lower, and even if the waveform of the pulse signal becomes dull due to the low temperature, the pulsed signal with a waveform that compensates for it becomes a semiconductor laser. It becomes possible to supply to.

  A laser driving device according to a seventh aspect is the laser driving device according to the fourth or fifth aspect, wherein the measuring means is a device for measuring a voltage value or a resistance value of the semiconductor laser. The second pulse generation unit further includes a correction peak value determining unit that determines the peak value of the second pulse signal in a monotonically increasing relationship according to the measurement value.

  In the laser driving device of the present invention, it is possible to measure the load variation due to temperature by measuring the voltage value or resistance value of the semiconductor laser. Further, even when the load is high and the waveform of the pulse signal becomes blunt, it becomes possible to supply a pulsed signal having a waveform that compensates for it to the semiconductor laser.

  The laser drive device according to claim 8 is the laser drive device according to any one of claims 4 to 7, wherein the digital signal includes at least a head pulse signal and a subsequent pulse signal corresponding to the number of consecutive pulses. It is converted to a multi-pulse signal. Further, the signal width of the second pulse signal is narrower than the width of the head pulse signal.

In the laser driving device of the present invention, it is possible to more appropriately compensate for the waveform blunting of the leading pulse signal.
The laser drive device according to claim 9 is the laser drive device according to claim 8, wherein the signal width of the second pulse signal added to the subsequent pulse signal is equal to the width of the subsequent pulse signal. Features.

In the laser driving device of the present invention, the signal width of the second pulse signal can be determined more easily, and the laser driving device can be configured more easily according to the signal width.
The laser drive device according to claim 10 is the laser drive device according to any one of claims 4 to 7, wherein the digital signal is converted into a pulse signal having a width corresponding to the continuous number. Features. Further, the signal width of the second pulse signal is narrower than the width of the pulse signal.

In the laser driving device of the present invention, it is possible to more appropriately compensate for the waveform blunting of the pulse signal.
The laser drive device according to claim 11 is the laser drive device according to any one of claims 4 to 10, wherein when the one-channel clock is T, the signal width of the second pulse signal is T / 8. The above is T / 4 or less.

In the laser driving device of the present invention, it is possible to generate the second pulse signal having a signal width shorter than the signal width of the pulse signal corresponding to the digital signal, and more appropriately compensate for the waveform blunting of the pulse signal. It becomes possible.
The laser drive device according to claim 12 is the laser drive device according to claim 5, wherein the third pulse signal is generated at a rising timing of the first pulse signal, and the fourth pulse signal is , Generated at the falling timing of the first pulse signal.

In the laser driving device of the present invention, it is possible to more appropriately compensate for the waveform dullness of the rising and falling edges of the first pulse signal.
A laser driving apparatus according to a thirteenth aspect is the laser driving apparatus according to any one of the first to third aspects, wherein the pulse generating means includes a pulse current source, a filter, and a filter control unit. The pulse current source outputs a pulse current according to the digital signal. The filter is a variable variable constant connected in parallel to the pulse current source. The filter control unit controls the constant of the filter according to the measured value.

With the laser driving device of the present invention, even if the load fluctuates due to the temperature fluctuation of the semiconductor laser, it is possible to generate an appropriate optical pulse waveform using a filter having a constant corresponding to the temperature fluctuation.
The laser drive device according to claim 14 is the laser drive device according to claim 13, wherein the filter control unit includes means for storing a constant of a filter to be controlled by the filter control unit in accordance with the measured value. .

With the laser driving device of the present invention, the filter control unit can acquire a filter constant corresponding to the measured value from the means for storing the filter constant, and generate an appropriate optical pulse waveform using the filter of the acquired filter constant. It becomes possible.
The laser driving device according to claim 15 is the laser driving device according to claim 13, wherein the filter includes a plurality of combinations of capacitors and switches connected in series.

The laser drive device according to claim 16 is the laser drive device according to claim 13, wherein the filter includes a plurality of combinations of capacitors, switches, and resistors connected in series.
The laser drive device according to claim 17 is the laser drive device according to claim 15, wherein the filter has a resistor inserted between a connection point between the capacitor and the switch and the ground. .

The laser drive device according to claim 18 is the laser drive device according to claim 16, wherein the filter includes a connection point when a capacitor, a switch, and a resistor are connected in series, and a ground. It is characterized by inserting a resistor between them.
The laser drive device according to claim 19 is the laser drive device according to any one of claims 13 to 19, wherein the filter can change the constant of the filter during reproduction during recording. To do.

The laser driving device according to claim 20 is the laser driving device according to claim 15 or 16, wherein at least one of the plurality of capacitors constituting the filter is connected to the outside of the integrated circuit. It is characterized by that.
With the laser driving device of the present invention, the integrated circuit can be made compact.

  A laser drive device according to a twenty-first aspect is the laser drive device according to the thirteenth aspect, wherein the measuring means is a device for measuring a voltage value of the semiconductor laser. The filter control unit includes a resistance calculation unit and a control execution unit. The resistance calculation means obtains the resistance value of the semiconductor laser from the operating voltage of the semiconductor laser and the operating current of the semiconductor laser. The control execution unit controls the constant of the filter according to the resistance value.

With the laser driving device of the present invention, even if the resistance value of the semiconductor laser fluctuates due to temperature fluctuation, it is possible to generate an appropriate optical pulse waveform using a filter having a constant corresponding to the temperature fluctuation.
The laser drive device according to claim 22 is the laser drive device according to claim 21, wherein the filter control unit includes means for storing a constant of a filter to be controlled by the control execution means in accordance with the resistance value. .

With the laser driving device of the present invention, the filter control unit can acquire a filter constant corresponding to the resistance value from the means for storing the filter constant, and generate an appropriate optical pulse waveform using the filter of the acquired filter constant. It becomes possible.
The optical disk device according to a twenty-third aspect includes an optical pickup and a disk drive device. The optical pickup includes a semiconductor laser that emits laser light, the laser driving device according to any one of claims 1 to 22, and an optical component that guides the laser light to an optical disk. The disk drive device drives the optical disk.

An optical disk apparatus according to the present invention includes the laser driving apparatus according to any one of claims 1 to 22. For this reason, it becomes possible to acquire the effect similar to each laser drive device.
A laser driving method according to a twenty-fourth aspect is a laser driving method for emitting a semiconductor laser in a pulsed manner in accordance with a digital signal, and includes a measuring step and a pulse generating step. In the measurement step, a measurement value that changes according to the temperature of the semiconductor laser is output. In the pulse generation step, a pulse signal having a shape corresponding to the measured value is output.

According to the laser driving method of the present invention, even when the load fluctuates due to the temperature fluctuation of the semiconductor laser, it is possible to appropriately perform pulsed light emission.
An integrated circuit for laser driving according to claim 25, which is a laser driving integrated circuit for emitting a semiconductor laser in a pulsed manner in response to a digital signal, comprising: a first pulse generating unit; a second pulse generating unit; And an adder. The first pulse generator generates a first pulse signal having a constant peak value. The second pulse generator generates a second pulse signal whose peak value changes in response to a measured value that changes according to the temperature of the semiconductor laser. The adder adds the first pulse signal and the second pulse signal and outputs a pulse signal.

With the laser driving integrated circuit of the present invention, for example, it is possible to compensate the first pulse signal corresponding to the digital signal with the second pulse signal corresponding to the measured value and output the pulse signal.
The integrated circuit for driving a laser according to claim 26 is an integrated circuit for driving a laser that emits a semiconductor laser in pulses in response to a digital signal, and includes a pulse current source, a filter, and a filter controller. Yes. The pulse current source outputs a pulse current according to the digital signal. The filter is a variable variable constant connected in parallel to the pulse current source. The filter control unit controls the constant of the filter corresponding to the measured value that changes according to the temperature of the semiconductor laser.

  With the laser driving integrated circuit of the present invention, even if the load fluctuates due to the temperature fluctuation of the semiconductor laser, an appropriate optical pulse waveform can be generated using a filter having a constant corresponding to the temperature fluctuation.

  According to the laser driving device of the present invention, the semiconductor laser can always emit light with the best pulse waveform regardless of the temperature, and the temperature margin in optical disc recording can be expanded.

Embodiments of the present invention will be described below with reference to the drawings.
In the embodiment of the present invention, a laser drive device capable of performing appropriate pulsed light emission even when a load change occurs due to a temperature change will be mainly described.
Before describing a specific device, the background of the invention that has been clarified by the inventor's investigation will be further described. According to the investigation by the present inventor, it has been found that the excess or deficiency of the compensation in the conventional configuration is caused by the fluctuation of the load due to the temperature fluctuation.

FIG. 1 shows an example of the temperature change of the series resistance in the red laser. FIG. 1 shows that the series equivalent resistance (Rs) increases abruptly when the temperature is below room temperature (= 25 °).
FIG. 2 shows an example of the temperature change of the series resistance in a blue laser mainly composed of GaN. As shown in FIG. 2, the blue laser has a high series equivalent resistance value (for example, about 15 to 25Ω) due to the structure, which is about 2 to 4 times that of the red laser. Further, the change in the value of the series resistance with respect to the temperature is larger than that of the red laser.

(Embodiment 1)
FIG. 3 is a block diagram of the laser driving apparatus according to Embodiment 1 of the present invention. In FIG. 3, the recording pulse generator 1 (first pulse generator) generates a constant pulse signal Sw having a constant peak value according to the digital signal (NRZ). Reference numeral 5 denotes a temperature sensor that measures temperature and outputs it as an electrical signal. The auxiliary pulse generator 4, the temperature compensation table 6, and the variable gain amplifier 7 constitute a second pulse generator that generates a correction pulse signal Sc whose peak value changes according to the measured temperature. Reference numeral 8 denotes an adder for adding the constant pulse signal Sw and the correction pulse signal Sc, and both signals are supplied to the semiconductor laser 3 through the current drive amplifier 2.

The recording pulse generator 1, auxiliary pulse generator 4, variable gain amplifier 7, adder 8, and temperature compensation table 6 constitute pulse generation means for outputting a pulse signal having a shape corresponding to the measured temperature. .
As shown in FIG. 4, the digital signal NRZ supplied to the laser driving device in the present embodiment is recorded by the recording pulse generator 1 at least the first pulse and the subsequent pulse corresponding to the number of consecutive digital signals “1”. It is converted into a multi-pulse (Sw) consisting of a group. Similarly, the correction pulse signal (Sc) is generated by the auxiliary pulse generator 4 or the like, and the signal width is narrower than the width of the head pulse signal. In FIG. 4, as an example, the interval of each pulse is a clock window Tw and the pulse width is Tw / 2. At this time, the pulse width of the auxiliary pulse signal is desirably Tw / 8 or more and Tw / 4 or less, as will be described later, and is Tw / 4 here. The correction pulse signal (Sc) is generated at the rising timing of the multi-pulse (Sw). As a result of this correction, a laser drive current IL having a waveform as shown in FIG. 4 is obtained. As a result, the laser emission waveform (dotted line in the figure) blunted by the laser load is improved (same solid line).

  A feature of the present invention is that the correction coefficient is variable according to temperature. That is, with respect to the temperature measured by the temperature sensor 5, the temperature compensation table 6 determines the coefficient K of the correction pulse in a monotonically decreasing relationship as shown in FIG. This monotonically decreasing function is related by the temperature characteristic of the equivalent resistance Rs of the semiconductor laser 3 as shown in FIG. This coefficient K is multiplied by the output signal of the auxiliary pulse generator 4 to generate a correction pulse signal (Sc) whose peak value changes according to the measured temperature. For example, as shown in FIG. 6, it is assumed that the equivalent series resistance Rs of the semiconductor laser at a temperature T = 25 ° C. is 5Ω and 2.5Ω at T = 50 ° C. (see FIG. 1). At this time, at T = 25 ° C., the correction is made so that the rise time and overshoot are less than the allowable values in order to compensate for the waveform blunting due to the time constant determined by Rs = 5Ω, equivalent load capacity C, and inductor L. The coefficient K = 0.5 is determined. On the other hand, when T = 50 ° C., the series equivalent resistance Rs of the semiconductor laser decreases to 2.5Ω, so that the load viewed from the current driving amplifier 2 becomes lighter and the blunting of the laser emission waveform tends to be reduced. At this time, if the drive current IL is supplied at K = 0.5, which is the same as when T = 25 ° C., overcorrection occurs, and as a result of occurrence of overshoot, the deterioration of the semiconductor laser is also accelerated.

  Therefore, in the present embodiment, when the series equivalent resistance Rs decreases at a high temperature, the correction coefficient K is also reduced according to the relationship shown in FIG. As a result, at T = 50 ° C., K = 0.25, and an appropriate laser emission waveform can be obtained with a light load.

(Embodiment 2)
The second embodiment of the present invention is applied to a recording / reproducing apparatus that generates a light emission waveform having a width corresponding to the number of consecutive digital signals NRZ. In the present embodiment, a device equivalent to the laser driving device in the first embodiment shown in FIG. 3 is used.

As shown in FIG. 7, the digital signal NRZ supplied to the laser driving device in the present embodiment is converted into a pulse signal (Sw having a width corresponding to the number of consecutive digital signals “1” by the recording pulse generator 1. ).
Similarly, the correction pulse signal (Sc) is generated by the auxiliary pulse generator 4 or the like, and the signal width is narrower than the width of the pulse signal. In FIG. 7, as an example, the interval of each pulse is a clock window Tw and the pulse width is Tw / 2. At this time, the pulse width of the auxiliary pulse signal is desirably Tw / 8 or more and Tw / 4 or less, as will be described later, and is Tw / 4 here. The correction pulse signal (Sc) is generated at the rising timing of the pulse signal (Sw). As a result of this correction, a laser drive current IL having a waveform as shown in FIG. 7 is obtained. As a result, the laser emission waveform (dotted line in the figure) blunted by the laser load is improved (same solid line).

  Similar to the first embodiment, the temperature compensation table 6 determines the coefficient K of the correction pulse in a monotonically decreasing relationship as shown in FIG. 5 with respect to the temperature measured by the temperature sensor 5. This monotonically decreasing function is related by the temperature characteristic of the equivalent resistance Rs of the semiconductor laser 3 as shown in FIG. This coefficient K is multiplied by the output signal of the auxiliary pulse generator 4 to generate a correction pulse signal (Sc) whose peak value changes according to the measured temperature. For example, as shown in FIG. 8, it is assumed that the equivalent series resistance Rs of the semiconductor laser at a temperature T = 25 ° C. is 5Ω and 2.5Ω at T = 50 ° C. (see FIG. 1). At this time, at T = 25 ° C., the correction is made so that the rise time and overshoot are less than the allowable values in order to compensate for the waveform blunting due to the time constant determined by Rs = 5Ω, equivalent load capacity C, and inductor L. The coefficient K = 0.5 is determined. On the other hand, when T = 50 ° C., the series equivalent resistance Rs of the semiconductor laser decreases to 2.5Ω, so that the load viewed from the current driving amplifier 2 becomes lighter and the blunting of the laser emission waveform tends to be reduced. At this time, if the drive current IL is supplied at K = 0.5, which is the same as when T = 25 ° C., overcorrection occurs, and as a result of occurrence of overshoot, the deterioration of the semiconductor laser is also accelerated.

  Therefore, in the present embodiment, when the series equivalent resistance Rs decreases at a high temperature, the correction coefficient K is also reduced according to the relationship shown in FIG. As a result, at T = 50 ° C., K = 0.25, and an appropriate laser emission waveform can be obtained with a light load.

(Embodiment 3)
The third embodiment of the present invention is implemented in a form provided with an auxiliary pulse generator B9 in order to compensate for the waveform blunting even when the laser emission waveform falls.
FIG. 9 is a block diagram of the laser driving apparatus according to the third embodiment. In FIG. 9, as in the first embodiment, the recording pulse generator 1 (first pulse generator) generates a constant pulse signal Sw having a constant peak value according to the digital signal (NRZ). Reference numeral 5 denotes a temperature sensor that measures temperature and outputs it as an electrical signal.

  The auxiliary pulse generator 4, the auxiliary pulse generator B9, the temperature compensation table 6, and the variable gain amplifiers 7 and 10 constitute a second pulse generation unit that generates a correction pulse signal whose peak value changes according to the measured temperature. In particular, the auxiliary pulse generator 4, the temperature compensation table 6, and the variable gain amplifier 7 constitute a third pulse generation unit that generates a correction pulse signal Sa whose peak value changes according to the measured temperature. In the present embodiment, the auxiliary pulse generator B9, the temperature compensation table 6, and the variable gain amplifier 10 further include a fourth pulse generator that generates a correction pulse signal Sb whose peak value changes according to the measured temperature. Configure. Reference numeral 8 denotes an adder for adding the constant pulse signal Sw and the correction pulse signals Sa and Sb, and both signals are supplied to the semiconductor laser 3 via the current drive amplifier 2.

The recording pulse generator 1, auxiliary pulse generator 4, auxiliary pulse generator B 9, variable gain amplifiers 7 and 10, adder 8, and temperature compensation table 6 output a pulse signal having a shape corresponding to the measured temperature. Pulse generation means is configured.
As shown in FIG. 10, the digital signal NRZ supplied to the laser driving apparatus in the present embodiment is recorded by the recording pulse generator 1 at least the first pulse and the subsequent pulse corresponding to the number of consecutive digital signals “1”. It is converted into a multi pulse (Sw) consisting of a group. Similarly, the auxiliary pulse generator 4 or the like generates a correction pulse signal (Sa) with reference to the rising edge of Sw, and the auxiliary pulse generator B9 or the like generates a correction pulse signal (with reference to the falling edge of Sw. Sb) is generated. The correction pulse signals Sa and Sb are characterized in that the signal width is narrower than the width of the head pulse signal. In FIG. 10, as an example, the interval between each pulse is a clock window Tw and the pulse width is Tw / 2. At this time, the pulse width of the auxiliary pulse signal is desirably Tw / 8 or more and Tw / 4 or less, as will be described later, and is Tw / 4 here. As a result of this correction, a laser drive current IL having a waveform as shown in FIG. 10 is obtained. As a result, the laser emission waveform (dotted line in the figure) blunted by the laser load is improved (same solid line).

  A feature of the present invention is that the correction coefficient is variable according to temperature. That is, with respect to the temperature measured by the temperature sensor 5, the temperature compensation table 6 determines the coefficient Ka of the rising correction pulse and the coefficient Kb of the falling correction pulse in a monotonically decreasing relationship as shown in FIG. This monotonically decreasing function is related by the temperature characteristic of the equivalent resistance Rs of the semiconductor laser 3 as shown in FIG. The coefficient Ka is multiplied by the output signal of the auxiliary pulse generator 4 to generate a correction pulse signal (Sa) whose peak value changes according to the measured temperature. Further, the coefficient Kb is multiplied by the output signal of the auxiliary pulse generator B9, and a correction pulse signal (Sb) whose peak value changes according to the measured temperature is generated. For example, as shown in FIG. 12, it is assumed that the equivalent series resistance Rs of the semiconductor laser at a temperature T = 25 ° C. is 5Ω and 2.5Ω at T = 50 ° C. (see FIG. 1). At this time, at T = 25 ° C., the correction coefficient is set so that the rise time and overshoot are less than the allowable values in order to compensate for the waveform dullness caused by the time constant determined by Rs = 5Ω, equivalent load capacity C, and inductor L. Ka = 0.5 is determined, and Kb = 0.5 is determined so that the fall time and undershoot are less than the allowable values. On the other hand, when T = 50 ° C., the series equivalent resistance Rs of the semiconductor laser decreases to 2.5Ω, so that the load viewed from the current driving amplifier 2 becomes lighter and the blunting of the laser emission waveform tends to be reduced. At this time, if the drive current IL is supplied at K = 0.5, which is the same as when T = 25 ° C., overcorrection occurs, and as a result of occurrence of overshoot, the deterioration of the semiconductor laser is also accelerated.

  Therefore, in the present embodiment, when the series equivalent resistance Rs decreases at a high temperature, the correction coefficients Ka and Kb are also decreased according to the relationship shown in FIG. As a result, at T = 50 ° C., Ka = 0.25 and Kb = 0.25, and an appropriate laser emission waveform can be obtained with a light load.

  In the third embodiment, the case where the semiconductor laser is caused to emit light by a multi-pulse including a leading pulse and a succeeding pulse group corresponding to the number of consecutive digital signals “1” has been described as an example. As described above, the present invention can also be applied to the case where the semiconductor laser emits light with a pulse having a width corresponding to the number of consecutive digital signals NRZ.

(Other matters regarding the first to third embodiments)
(1)
In the first to third embodiments, the monotonically decreasing function of the correction coefficient K (Ka and Kb in the third embodiment) is related to the temperature characteristic of the equivalent resistance Rs of the semiconductor laser 3, but there are various A method is conceivable.

For example, the laser may be pulsed while changing the ambient temperature, the correction coefficient K may be obtained so that the rise time and overshoot are less than the allowable values, and the relationship between the temperature and the correction coefficient K may be obtained. Further, the same experiment may be performed on a plurality of samples, and the relationship between the representative temperature and the correction coefficient K may be given to the correction table. When the temperature characteristic of the equivalent resistance Rs is a function Rs (T) of the temperature T, the correction coefficient K has a component proportional to this Rs (T).
K (T) = α1 × Rs (T) + β1
(Where α1 and β1 are constants). Also, when the equivalent resistance Rs is in a relationship that is almost inversely proportional to the temperature,
K (T) = α2 / T + β2
(Where α2 and β2 are constants).

(2)
In the first and third embodiments, the pulse width of the auxiliary pulse signal is narrower than the leading pulse width and is Tw / 8 or more and Tw / 4 or less, but there is a reason for this. If the pulse width of the auxiliary pulse signal is too narrow, waveform blunting cannot be corrected. Therefore, the pulse width needs to be at least Tw / 8 or more. Further, if the pulse width is wide, overcorrection occurs, and waveform distortion occurs as shown in FIG. In order to avoid this waveform distortion, it is preferable to set the pulse width to at least the leading pulse width and further to Tw / 4 or less.

These are merely examples, and the pulse width of the auxiliary pulse signal may be freely selected as long as it is equal to or less than the head pulse width.
In the second embodiment, the pulse width of the auxiliary pulse signal is narrower than that of the constant pulse signal Sw and is Tw / 8 or more and Tw / 4 or less. This is also the same reason as described above. If the pulse width of the auxiliary pulse signal is too narrow, waveform blunting cannot be corrected. Therefore, the pulse width needs to be at least Tw / 8 or more. If the pulse width is wide, overcorrection occurs and waveform distortion occurs. In order to avoid this waveform distortion, it is preferable to make the pulse width at least narrower than the constant pulse signal Sw and set it to Tw / 4 or less.

  As shown in FIG. 15, when the width of the subsequent pulse is narrower than the leading pulse, the width of the correction pulse to be added to the subsequent pulse can be made equal to the width of the subsequent pulse to appropriately correct the waveform blunting. It is preferable to do so. In this case, it is not necessary to provide means for changing the pulse width of the auxiliary pulse in various ways, and the configuration of the apparatus can be simplified.

(3)
In Embodiments 1 to 3, the case where the red laser is driven has been described as an example, but the present invention is not limited to this.
As shown in FIG. 2, a blue laser mainly composed of GaN has a high series equivalent resistance value, which is about 2 to 4 times that of a red laser. Waveform blunting due to a high series equivalent resistance value at a low temperature. The phenomenon is expected to appear more prominently. The present invention can be expected to be effective when applied to such a blue laser.

(4)
In the first to third embodiments, it has been described that the coefficient K of the correction pulse is determined from the temperature compensation table 6 based on the measurement value measured using the temperature sensor.
Here, the temperature measured by the temperature sensor is preferably the temperature of the semiconductor laser, but may be the temperature in the environment where the semiconductor laser is installed.

Further, the correction pulse coefficient K may be determined based on a measured value other than temperature.
An example is shown in FIG. FIG. 16 is provided with means for determining the correction pulse coefficient K based on the resistance value calculated from the operating voltage of the semiconductor laser in place of the temperature sensor 5 and the temperature compensation table 6 described with reference to FIG. . In FIG. 16, the same reference numerals are given to the same components as those in FIG. In the following, a description will be given focusing on the parts different from FIG.

  The laser drive device shown in FIG. 16 includes a voltage detection circuit 11, a resistance calculator 12, and a compensation table 13. The voltage detection circuit 11 is connected to the current drive amplifier 2 and measures the operating voltage of the semiconductor laser. The resistance calculator 12 calculates the resistance value of the semiconductor laser from the operating voltage detected by the voltage detection circuit 11 and the operating current of the semiconductor laser. The compensation table 13 stores a correction pulse coefficient K for each resistance value, and outputs a correction pulse coefficient K corresponding to the calculated resistance value. Here, the table stored in the compensation table 13 stores a coefficient K that monotonously increases with respect to the resistance value.

The voltage detection circuit 11 and the resistance calculator 12 do not need to be configured by different parts, and may be a device that can directly acquire the resistance value of the semiconductor laser.
The compensation table 13 may store a correction pulse coefficient K for the voltage value, and may directly output the coefficient K for the voltage value detected by the voltage detection circuit 11.

(5)
Each functional block and hardware configuration in the block diagram are typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

For example, the recording pulse generator 1, auxiliary pulse generator 4, adder 8, variable gain amplifier 7, current drive amplifier 2, etc. in FIG. 3 may be integrated into a single chip (within the one-dot chain line in FIG. 3).
Further, for example, the recording pulse generator 1, the auxiliary pulse generator 4, the adder 8, the variable gain amplifier 7, the auxiliary pulse generator B9, the variable gain amplifier 10, the current drive amplifier 2 and the like in FIG. It is also possible (within the alternate long and short dash line in FIG. 9).

The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.
Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of the circuit cells inside the LSI may be used.

Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.
(Embodiment 4)
FIG. 17 is a block diagram of a laser drive circuit according to Embodiment 4 of the present invention. The laser drive circuit according to the present invention performs a pulse current source 100 for supplying a pulse current to the semiconductor laser 150 according to a recording signal, a high frequency signal source 140 for supplying a high frequency current to the semiconductor laser, and waveform equalization of the semiconductor laser. The variable filter 120, a temperature sensor 160 that measures temperature, and a filter control unit 170 that controls constants of the variable filter are included.

The pulse current source 100 and the variable filter 120 constitute pulse generating means for outputting a pulse signal having a shape corresponding to the measured temperature.
A more detailed main configuration of the laser drive circuit will be described with reference to FIG. In FIG. 18, the laser drive circuit 110 surrounded by the dotted line is assumed to be realized by an integrated circuit.

In FIG. 18, reference numerals 101 to 104 denote current sources for causing the semiconductor laser 150 to emit light with a desired light intensity. The current source 101 supplies a current Ir to the semiconductor laser.
The current source 102 supplies the current Ib according to the recording signal W2. Similarly, the current source 103 supplies the current Ie according to the recording signal W3, and the current source 104 supplies the current Ip according to the recording signal W4.

The high-frequency signal source 140 superimposes and supplies a high-frequency current to the DC current Ir in order to suppress so-called scoop noise that occurs when reflected light from the optical disk returns to the semiconductor laser during information reproduction.
Here, an operation sequence during information reproduction and recording will be described with reference to FIG. At the time of reproduction, since the recording signals W 2 to W 4 are at the L level, only the current source 101 among the current sources 101 to 104 supplies current to the semiconductor laser 150. Further, a high frequency current from the high frequency signal source 140 is superimposed.

  When recording information, the following operations are performed. When forming a recording mark and a recording space as shown in FIG. 19A on a recording track, an optical pulse train modulated with a peak level, a bottom level, and a bias level as shown in FIG. Need to be irradiated. For this reason, currents Ir, Ib, Ie, and Ip are added in accordance with the recording signals W2 to W4 to generate a pulse current as shown in FIG. 19C, which is supplied to the semiconductor laser. By this operation, an optical pulse subjected to desired intensity modulation as shown in FIG. 19B is generated.

  Capacitors 121 to 124 and MOS transistors 125 to 128 are high-pass filters for optimizing the optical pulse waveform. The optical pulse waveform is a waveform having ringing due to the influence of the inductor of the wiring between the semiconductor laser 150 and the laser driving circuit 110. In order to suppress this ringing and obtain an appropriate optical pulse waveform, the filter is provided.

Assuming that the capacities of the capacitors 121, 122, 123, and 124 are C1, C2, C3, and C4, C2 to C4 are respectively set.
C2 = 2 × C1
C3 = 4 × C1
C4 = 8 × C1
To be. For example, when C1 = 5 pF, C2 = 10 pF, C3 = 20 pF, and C4 = 40 pF. With such a configuration, the constant Cc of the high-pass filter can be selected from 16 types with a resolution of 5 pF from 0 pF to 75 pF. This selection is performed by ON / OFF control of the MOS switches 125 to 128 according to the signals S1 to S4.

  If the bypass filter is operated at the time of reproduction, the amplitude of the superimposed high-frequency current is reduced, and the return light noise is increased, which may cause the reproduction performance of the optical disc apparatus to deteriorate. Therefore, at the time of reproduction, the capacitors 121 to 124 are not operated as a high-pass filter. Therefore, when W2 is Lo (that is, at the time of reproduction) by the AND gates 129 to 132, all the signals are selected regardless of the logic of the selection signals S1 to S4. The MOS switch is turned off.

Here, for the purpose of reducing the increase in the area of the integrated circuit, the largest capacitor 124 is externally attached to the integrated circuit.
The feature of the present invention is that the constant Cc of the high-pass filter is changed depending on the temperature. The EEP-ROM 172 stores a characteristic table of constants (Cc) of a high-pass filter that can obtain an optimum optical pulse waveform with respect to the temperature measured by the temperature sensor, as shown in FIG. In the table, the constant Cc of the high-pass filter is determined to increase as the temperature increases. In this table, the series resistance Rs in the equivalent circuit of the semiconductor laser 150 shown in FIG. 21A is related by the temperature characteristic of FIG. 21B (decreasing as the temperature increases). The microcomputer 171 selects the constant Cc of the high-pass filter corresponding to the temperature measured by the temperature sensor by referring to the table of the EEP-ROM 172, determines the logic of the signals S1 to S4, and controls the MOS switches 125 to 128. Do.

  For example, as shown in FIG. 22, it is assumed that the series resistance Rs of the semiconductor laser when the temperature T = 25 ° C. is 20Ω (see FIG. 21B). At this time, at T = 25 ° C., the equivalent circuit of the semiconductor laser as shown in FIG. 21A, that is, ringing of the optical pulse waveform due to the time constant determined by Rs = 20Ω, capacitance C, and inductor L is compensated. Therefore, the constant of the high-pass filter is selected as Cc = 25 pF so that the rise time and the overshoot are less than the allowable values. On the other hand, when T = 0 ° C., the series resistance Rs of the semiconductor laser is reduced to 30Ω, so if the constant of the high-pass filter is the same as when T = 25 ° C., the optical pulse waveform is as shown in FIG. Significantly slows down. Further, when T = 50 ° C., the series resistance Rs of the semiconductor laser is reduced to 15Ω, so if the constant of the high-pass filter is the same as when T = 25 ° C., the overshoot of the optical pulse waveform is as shown in FIG. As shown in FIG. There is a possibility that the quality of the recording signal is deteriorated due to the temperature change of the optical pulse waveform.

  Therefore, in this embodiment, when the series resistance Rs increases at a low temperature, the constant of the high-pass filter is also decreased to Cc = 0 pF accordingly. Further, when the series resistance Rs decreases at a high temperature, the constant of the high pass filter is also increased to Cc = 40 pF accordingly. As a result, as shown in FIGS. 22D and 22F, it is possible to obtain an appropriate optical pulse waveform in which the overshoot amount is controlled within an allowable value at both low and high temperatures.

In this embodiment, the capacitors 121 to 123 are incorporated in the integrated circuit and the capacitor 124 is attached to the outside of the integrated circuit. However, the present invention is not limited to this embodiment. If the area of the integrated circuit is acceptable, all capacitors may be incorporated in the integrated circuit.
In the present embodiment, the high-pass filter is configured with a capacitor, but the present invention is not limited to this embodiment. For example, the same effect can be obtained by using a high-pass filter configuration in which a resistor is inserted in series with a capacitor as shown in FIG. Further, as shown in FIG. 24, a plurality of sets of resistors and MOS switches may be connected to one capacitor, and the filter characteristics may be varied by changing the resistance value. In addition, as shown in FIG. 25, the gate voltage of the MOS switch 322 may be controlled by the output voltage of the DA converter 321 to change the on-resistance value of the MOS switch.

  In addition, at the moment when at least one of the MOS switches 125 to 128 is turned on, a current may suddenly flow to charge the capacitor. Since this current is supplied from the anode power supply of the semiconductor laser, there is a possibility that the laser flows and damages the worst laser. In order to avoid this, it is preferable to connect pull-down resistors 401 to 404 to nodes to which capacitors and MOS switches are connected as shown in FIG.

  In this embodiment, the laser drive circuit 110 in the region surrounded by the dotted line in FIG. 18 is realized by an integrated circuit, but the present invention is not limited to this embodiment. For example, as shown in FIG. 27, if the temperature sensor, the microcomputer, the EEP-ROM, etc. are built in the integrated circuit, it is possible to reduce the number of parts on the pickup, realize a low cost, The number can be reduced and the pickup can be simplified. Further, (other matters concerning the first to third embodiments) the matters described in (5) are the same for the present embodiment.

(Embodiment 5)
In the fifth embodiment, the optical resistance is obtained by directly determining the series resistance value Rs of the semiconductor laser from the operating voltage and drive current of the semiconductor laser and changing the constant Cc of the high-pass filter in accordance with the series resistance value Rs. Implemented in an optimally controlled manner.

  FIG. 28 is a block diagram of a laser drive circuit according to Embodiment 5 of the present invention. The laser drive circuit according to the present invention equalizes a laser waveform, a pulse current source 100 that supplies a pulse current to the semiconductor laser 150 according to a recording signal, a high-frequency signal source 140 that supplies a high-frequency current to the semiconductor laser 150, and a laser. The variable filter 120 includes a voltage detection circuit 200 that detects the operating voltage of the semiconductor laser, and a filter control unit 210 that controls constants of the variable filter.

The pulse current source 100 and the variable filter 120 constitute pulse generating means for outputting a pulse signal having a shape corresponding to the operating voltage.
A more detailed configuration of the laser drive circuit will be described with reference to FIG. The same components as those in FIG. 18 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 29, an A / D converter 203 and resistors 201 and 202 constitute a semiconductor laser operating voltage detection circuit. The resistors 201 and 202 divide the output terminal voltage Vout of the laser driving circuit. If the resistance values of the resistors 201 and 202 are set equal (for example, 10 kΩ each), the detection voltage Vdet of the A / D converter is
Vdet = Vout / 2 (Formula 1)
It becomes. On the other hand, the operating voltage Vop of the semiconductor laser is E, where the power supply voltage at the anode of the semiconductor laser is E.
Vop = E−Vout (Formula 2)
It is.

Therefore, from (Equation 1) and (Equation 2),
Vop = E−2 × Vdet (Equation 3)
Therefore, the operating voltage of the semiconductor laser can be obtained by detecting Vdet.

Further, the arithmetic DSP 211 obtains the series resistance value Rs of the semiconductor laser from the detected voltage and the drive current. For example, the operating voltage Vb when the DC light is emitted with the bottom power is detected, the operating voltage Ve when the DC light is emitted with the bias power is further detected, and the operating voltage between the bottom power and the bias power is detected. The difference ΔVop is
ΔVop = Ve−Vb
I ask. The drive current ΔIop between the bottom power and the bias power is
ΔIop = Ie
Therefore, the series resistance value Rs of the semiconductor laser is
Rs = ΔVop / ΔIop
Can be obtained as

  The ER-ROM 212 stores a characteristic table of constants of a high-pass filter that can obtain an optimum optical pulse waveform with respect to the series resistance value Rs of the semiconductor laser as shown in FIG. The arithmetic DSP selects the high-pass filter constant Cc that is optimal for the series resistance value Rs of the semiconductor laser by referring to the EEP-ROM.

  With this configuration, even if the temperature changes and the series resistance value Rs of the semiconductor laser changes, an appropriate optical pulse waveform in which the overshoot amount is controlled within an allowable value can be obtained. That is, it becomes possible to correct the light emission power of the semiconductor laser according to the resistance value of the semiconductor laser.

(Other matters regarding Embodiments 4 to 5)
(1)
The matters described in Embodiments 1 to 5 can be used in appropriate combination. For example, the configuration for detecting the operating voltage of the semiconductor laser described in Embodiment Mode 5 can be applied to the laser driving device described with reference to FIG.

  The laser driving device according to the present invention has good pulse emission characteristics independent of temperature, and is useful as a DVD recording / reproducing device or the like.

Diagram showing the relationship between series equivalent resistance and temperature in a red laser Diagram showing the relationship between series equivalent resistance and temperature in blue laser Main configuration diagram of laser driving apparatus according to Embodiment 1 and Embodiment 2 of the present invention Operation sequence diagram of laser driving apparatus according to Embodiment 1 of the present invention The figure which shows the relationship between the correction coefficient K and temperature The figure which shows the correction coefficient K in each temperature, the series resistance Rs, the laser drive current IL, and a laser emission waveform. Operation sequence diagram of laser driving apparatus in Embodiment 2 of the present invention The figure which shows the correction coefficient K in each temperature, the series resistance Rs, the laser drive current IL, and a laser emission waveform. Main configuration diagram of laser driving apparatus according to Embodiment 3 of the present invention Operation sequence diagram of laser driving apparatus according to Embodiment 3 of the present invention The figure which shows the relationship between correction coefficient Ka and Kb, and temperature The figure which shows the correction coefficient K in each temperature, the series resistance Rs, the laser drive current IL, and a laser emission waveform. Operation sequence diagram when the laser driving device according to the third embodiment of the present invention is applied to the case where the semiconductor laser emits light with a pulse having a width corresponding to the number of consecutive digital signals NRZ. Diagram showing the waveform distortion that occurs when the correction pulse width is increased. Operation sequence diagram when the correction pulse width added to the subsequent pulse is made equal to the width of the subsequent pulse The main block diagram of the laser drive device in another embodiment of this invention Block diagram of a laser drive circuit in Embodiment 4 of the present invention Main configuration diagram of laser driving circuit according to Embodiment 4 of the present invention Operation sequence diagram of laser drive circuit in Embodiment 4 of the present invention Diagram showing temperature and high-pass filter constant to be selected (A) Diagram showing equivalent circuit of semiconductor laser (b) Diagram showing temperature dependence of semiconductor laser series resistance Diagram showing the relationship between temperature and optical pulse waveform The block diagram of the filter in another embodiment of this invention The block diagram of the filter in another embodiment of this invention The block diagram of the filter in another embodiment of this invention The block diagram of the filter in another embodiment of this invention The main block diagram of the laser drive circuit in another embodiment of this invention Block diagram of a laser drive circuit in Embodiment 5 of the present invention Main configuration diagram of laser driving circuit according to Embodiment 5 of the present invention Diagram showing semiconductor laser resistance and high-pass filter constant to be selected Main configuration diagram of laser drive device in background art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording pulse generator 2 Current drive amplifier 3 Semiconductor laser 4 Auxiliary pulse generator 5 Temperature sensor 6 Temperature compensation table 7 Variable gain amplifier 8 Adder 9 Auxiliary pulse generator B
DESCRIPTION OF SYMBOLS 10 Variable gain amplifier 100 Pulse current source 101 Current source 102-104 Pulse current source 120 Variable filter 121-124 Capacitor 125-128 MOS transistor 129-132 AND gate 140 Voltage control oscillator 150 Semiconductor laser 160 Temperature sensor 170 Filter control part 171 Microcomputer 172 EEPROM-ROM

Claims (26)

A laser driving device that emits a semiconductor laser in pulses in response to a digital signal,
Measurement means for outputting a measurement value that changes according to the temperature of the semiconductor laser;
Pulse generating means for outputting a pulse signal having a shape corresponding to the measured value;
A laser driving device. The measuring means is a device for measuring the temperature of the semiconductor laser;
The laser driving device according to claim 1. The measuring means is a device for measuring a voltage value or a resistance value of the semiconductor laser.
The laser driving device according to claim 1. The pulse generating means includes a first pulse generating unit that generates a first pulse signal having a constant peak value, and a second pulse that generates a second pulse signal whose peak value changes according to the measured value. A generator, and an adder that adds the first pulse signal and the second pulse signal to output the pulse signal.
The laser drive device according to claim 1. The second pulse generation unit includes a third pulse generation unit that generates a third pulse signal that is a forward signal with respect to the first pulse signal and whose peak value changes according to the measurement value. A fourth pulse generating unit that generates a fourth pulse signal that is a signal in the opposite direction to the first pulse signal, and whose peak value changes according to the measurement value.
The laser driving device according to claim 4. The measuring means is a device for measuring the temperature of the semiconductor laser;
The second pulse generation unit further includes correction peak value determination means for determining a peak value of the second pulse signal in a monotonically decreasing relationship according to the measurement value,
The laser drive device according to claim 4 or 5. The measuring means is a device for measuring a voltage value or a resistance value of the semiconductor laser,
The second pulse generation unit further includes correction peak value determination means for determining a peak value of the second pulse signal in a monotonically increasing relationship according to the measurement value,
The laser drive device according to claim 4 or 5. The digital signal is converted into a multi-pulse signal composed of at least a leading pulse signal and a subsequent pulse signal corresponding to the number of consecutive pulses,
The signal width of the second pulse signal is narrower than the width of the head pulse signal,
The laser drive device according to claim 4. The signal width of the second pulse signal added to the subsequent pulse signal is equal to the width of the subsequent pulse signal.
The laser driving device according to claim 8. The digital signal is converted into a pulse signal having a width corresponding to the continuous number,
The signal width of the second pulse signal is narrower than the width of the pulse signal,
The laser drive device according to claim 4. When the one-channel clock is T, the signal width of the second pulse signal is T / 8 or more and T / 4 or less,
The laser drive device according to any one of claims 4 to 10. The third pulse signal is generated at the rising timing of the first pulse signal,
The fourth pulse signal is generated at the falling timing of the first pulse signal.
The laser driving device according to claim 5. The pulse generation means includes a pulse current source that outputs a pulse current in accordance with the digital signal, a filter that is connected in parallel to the pulse current source, and a variable constant, and the filter in accordance with the measured value. A filter control unit for controlling a constant;
The laser drive device according to claim 1. The filter control unit includes means for storing a constant of a filter to be controlled by the filter control unit according to the measurement value,
The laser driving device according to claim 13. The filter includes a plurality of combinations of capacitors and switches connected in series,
The laser driving device according to claim 13. The filter includes a plurality of combinations of capacitors, switches, and resistors connected in series.
The laser driving device according to claim 13. The filter is characterized in that a resistor is inserted between a connection point between the capacitor and the switch and a ground.
The laser driving device according to claim 15. The filter is characterized in that a resistor is inserted between one connection point when the capacitor, the switch, and the resistor are connected in series, and a ground.
The laser driving device according to claim 16. The filter is characterized in that, during reproduction, the constant of the filter can be changed from that during recording.
The laser drive device according to any one of claims 13 to 19. Of the plurality of capacitors constituting the filter, at least one of the capacitors is connected to the outside of the integrated circuit.
The laser driving device according to claim 15 or 16. The measuring means is a device for measuring a voltage value of the semiconductor laser;
The filter control unit includes a resistance calculation unit that obtains a resistance value of the semiconductor laser from an operating voltage of the semiconductor laser and an operating current of the semiconductor laser, and a control execution unit that controls a constant of the filter according to the resistance value. Including,
The laser driving device according to claim 13. The filter control unit includes means for storing a constant of a filter to be controlled by the control execution means in accordance with the resistance value.
The laser driving device according to claim 21. An optical pickup comprising a semiconductor laser that emits laser light, the laser driving device according to claim 1, and an optical component that guides the laser light to an optical disc,
A disk drive device for driving the optical disk;
An optical disc device comprising: A laser driving method for emitting a semiconductor laser in pulses according to a digital signal,
A measurement step of outputting a measurement value that varies depending on the temperature of the semiconductor laser;
A pulse generation step of outputting a pulsed signal having a shape corresponding to the measured value;
A laser driving method comprising: A laser driving integrated circuit for emitting a semiconductor laser in a pulsed manner in response to a digital signal,
A first pulse generator for generating a first pulse signal having a constant peak value;
A second pulse generator for generating a second pulse signal whose peak value changes in response to a measured value that changes according to the temperature of the semiconductor laser;
An adder for adding the first pulse signal and the second pulse signal to output a pulse signal;
An integrated circuit for driving a laser. A laser driving integrated circuit for emitting a semiconductor laser in a pulsed manner in response to a digital signal,
A pulse current source that outputs a pulse current in response to the digital signal;
A variable-variable filter connected in parallel to the pulse current source;
A filter control unit for controlling a constant of the filter in response to a measurement value that changes according to the temperature of the semiconductor laser;
An integrated circuit for driving a laser.

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