JPH08274395A - Semiconductor laser drive method, and semiconductor laser deterioration judge method, and semiconductor laser driver - Google Patents

Abstract

PURPOSE: To provide a semiconductor laser drive method, which can stably output a plurality of pulses including short pulses μmsec order in pulse width by keeping the optical output constant with accuracy, using an inexpensive semiconductor laser driver, a semiconductor laser deterioration judge method, and the semiconductor laser driver. CONSTITUTION: A photodiode 2 and an APC circuit 4 monitor the rate of change of a laser diode 1 at output of long pulses; and the data obtained by this is inputted into an ACC control circuit 6 storing the data related to the operation property the laser diode, and also the ACC control circuit 6 infers the deterioration of the operation property of the laser diode 1 at the time of output of short pulses, based on the data. Together with it, it finds out a drive current required for compensating the deteriorated output, and controls the output at the time of short pulse output operation mode of the laser diode driving circuit 3 to be constant currents, using the ACC circuit 5, with this drive current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser driving method, a semiconductor laser deterioration judging method, and a semiconductor laser driving device, and more particularly to a semiconductor laser driving method having a plurality of pulse output operation modes including a short pulse output operation. , A semiconductor laser deterioration determination method, and a semiconductor laser drive device.

[0002]

2. Description of the Related Art FIG. 6 is a diagram for explaining a conventional semiconductor laser driving method having a plurality of pulse output operation modes including a short pulse output operation, and schematically shows a circuit configuration of a semiconductor laser driving device. It is the figure shown. In the figure, 1 is a laser diode, 2 is a monitor photodiode,
3 is a laser diode drive circuit that supplies a predetermined drive current to the laser diode 1, 4 is a constant light output control (auto power control) circuit (hereinafter referred to as APC circuit),
Reference numeral 9 is a drive control circuit for controlling the output timing of the laser diode drive circuit 3. In this semiconductor laser driving device, the laser diode 1 is connected to the laser diode driving circuit 3, the photodiode 2 is arranged at a position where the emitted light of the laser diode 1 can be monitored, and the output of the photodiode 2 is APC circuit 4. The output of the APC circuit 4 is connected to the laser diode drive circuit 3. In addition, the drive control circuit 9
Is connected to the laser diode drive circuit 3.

FIG. 7 is a diagram showing the relationship between the optical output waveform (FIG. 7 (a)) and the drive current waveform (FIG. 7 (b)) of the semiconductor laser according to the conventional semiconductor laser driving method. In (a), the vertical axis represents the light output and the horizontal axis represents the time.
In, the vertical axis represents drive current and the horizontal axis represents time.
Further, a is a short pulse having a short pulse width, b is a long pulse having a long pulse width, P2 is an optical output of a short pulse a, P1 is an optical output of a long pulse b, ta is a pulse width of a short pulse a, and tb is a long pulse. The pulse width of the pulse b is shown. Reference numeral 11 denotes a drive current when the laser diode 1 has a normal operation characteristic, and reference numeral 12 denotes a drive current when the operation characteristic of the laser diode 1 is deteriorated.

Next, a conventional semiconductor laser driving method will be described with reference to FIG.
The case of outputting two pulses consisting of a short pulse a and a long pulse b used for firing the optical thyristor as shown in FIG. When a signal is sent from the drive control circuit 9 to the laser diode control circuit 3 at a timing matched with the pulse widths ta and tb of the short pulse a and the long pulse b, the laser diode drive circuit 3 drives the drive current 11 by this signal. , That is, the drive currents I1 and I2 are output,
The laser diode 1 outputs laser light having optical outputs P1 and P2. The light outputs P1 and P2 are received by the monitor photodiode 2, and the output of the photodiode 2 is input to the APC circuit 4. This APC circuit 4 is
The monitor photodiode 2 is used to monitor the amount of change in the optical output of the laser diode 1 received, and based on this, a signal for correcting the optical output of the laser diode 1 to the original output is provided. The output is fed back to the laser diode drive circuit 3 to control the output of the laser diode drive circuit 3 constant. Normally, the laser diode generates heat depending on the operating time and its quality deteriorates, and as a result, the optical output decreases. However, it is necessary to correct the drive current, but by providing such an APC circuit 4, it becomes possible to operate while maintaining the optical output from the laser diode 1 at a predetermined value, and to cope with changes in the output of the laser diode 1. As a result, a highly accurate pulse having a stable light output can be obtained. Here, while the laser diode 1 is outputting the short pulse a (or the long pulse b), the APC circuit 4
Constantly monitors the amount of change in the optical output of the laser diode 1 so that the optical output becomes P2 (or P1), and feeds back the monitoring result to control the laser diode drive circuit 3. When a change in the optical output P2 (or the optical output P1) is monitored while the short pulse a (or the long pulse b) is being output, the APC circuit 4 corrects the output of the laser diode drive circuit 3, The drive circuit 12 outputs a drive current 12 that keeps the optical output P2 (or the optical output P1), that is, the drive current I'2 (or the drive current I'1).

[0005]

The conventional semiconductor laser driving method uses the semiconductor laser driving device having the above-described configuration, and the optical output of the laser diode 1 received by the photodiode 2 is monitored by the APC circuit 4. The result of this monitoring is fed back to the laser diode drive circuit 3 to control the optical output to obtain a pulse output in which the optical output is maintained constant with high accuracy.

However, in the case of performing an optical output operation in which a plurality of pulses having different pulse widths are combined as described above, one of the plurality of pulses is a short pulse having a very short pulse width on the order of μsec. In some cases, the deterioration of the laser diode is instantaneously received by the monitoring photodiode while the short pulse is being output and is monitored by the APC circuit, and the feedback to the laser diode drive circuit is quickly performed by the circuit design or the element. It is very difficult in terms of characteristics. Usually, in order to monitor such a change in the optical output of a short pulse at high speed and feed it back, an element having excellent high-speed response is used as a light-receiving element such as a monitor photodiode, and a transistor in the APC circuit is used. A method of improving the high-speed response of the laser drive device by using an element having excellent high-speed response as the element such as
Since there is a problem that the cost of the driving device is high because it is extremely expensive compared to a normal element, and since the high-speed response of such an element is limited, it is considered that such an element is used. However, if the pulse width becomes very short, A
There is a problem that it is difficult to perform accurate constant light output control using a PC circuit, and it is difficult to obtain a pulse having a stable light output.

Further, in the laser diode driving method for outputting such a short pulse, since it is difficult to detect the deterioration of the optical output of the short pulse as described above, the short pulse output operation mode of the laser diode is detected. Even when the laser operating characteristics at the time are completely deteriorated,
There is a problem that it is very difficult to judge this deterioration.

The present invention has been made to solve the above problems, and an inexpensive semiconductor laser driving device is used to output a plurality of pulses including a short pulse having a pulse width of the order of μsec. An object of the present invention is to provide a semiconductor laser driving method capable of maintaining a constant value with high accuracy and stable output.

Further, the present invention has been made to solve the above problems, and it is possible to determine the deterioration of the characteristics of the laser diode even when performing a pulse output operation including a pulse of the order of μsec. An object of the present invention is to provide a semiconductor laser deterioration determination method.

Further, the present invention has been made to solve the above problems, and stabilizes a plurality of pulses including a short pulse having a pulse width of the order of μsec by keeping the optical output with a high precision. It is an object of the present invention to provide an inexpensive semiconductor laser drive device capable of outputting as an output.

[0011]

A semiconductor laser driving method according to the present invention is a method for driving a laser diode in a plurality of pulse output operation modes having different pulse widths, wherein the pulse width of the plurality of pulse output operation modes is The plurality of pulse outputs are monitored based on the amount of change in the laser light output monitored by the monitored amount of change in the laser light output of the laser diode in the large long pulse output operation mode and the previously stored data regarding the characteristics of the laser diode. The change amount of the laser light output of the laser diode in the short pulse output operation mode with a small pulse width among the operation modes is estimated, and the current for driving the laser diode in the short pulse output operation mode is the estimated laser light output. Constant current control so that the drive current is corrected for the amount of change in Serial is the light output of the short-pulse output operation mode of the laser diode in which a constant.

Further, in the above semiconductor laser driving method, constant light output control is performed so that the current for driving the laser diode during the long pulse output operation becomes a driving current in which the amount of change in the monitored laser light output is corrected. Then, the light output of the laser diode in the long pulse output operation mode is made constant.

Further, a semiconductor laser deterioration judging method according to the present invention is a method for judging deterioration of a laser diode driven in a plurality of pulse output operation modes having different pulse widths. The amount of change in the laser light output of the laser diode in a long-pulse output operation mode having a large width is monitored, and from the monitored amount of change in the laser light output and data stored in advance regarding the characteristics of the laser diode, The amount of change in the laser light output of the laser diode in the short pulse output operation mode with a small pulse width in the pulse output operation mode is estimated, and from the amount of change in the optical output in the long pulse and short pulse output operation modes, Start pulse output operation of optical output in long pulse and short pulse output operation mode The rate of change of the demand, and the displacement rate,
The deterioration state of the laser diode is determined from prestored data relating to the characteristics of the laser diode, and the determination result is output to the outside.

Further, the semiconductor laser driving device according to the present invention is a semiconductor laser driving device for driving a laser diode in a plurality of pulse output operation modes having different pulse widths, and the pulse width is large among the plurality of pulse output operation modes. From the monitor means for monitoring the change amount of the laser light output of the laser diode in the long pulse output operation mode, the change amount of the monitored laser light output, and the previously stored data relating to the characteristic of the laser diode, Change amount estimating means for estimating a change amount of the laser light output of the laser diode in a short pulse output operation mode having a small pulse width in the pulse output operation mode, and a current for driving the laser diode in the short pulse output operation mode Compensates for the amount of change in the laser light output estimated above. And constant current control so that the drive current, in which a constant-current control means for a constant light output of the short-pulse output operation mode of the laser diode.

Further, in the semiconductor laser driving device, constant light output control is performed so that the current for driving the laser diode during the long pulse output operation is a driving current corrected for the amount of change in the monitored laser light output. The laser diode is provided with a constant light output control means for making constant the light output in the long pulse output operation mode.

In the semiconductor laser driving device, the pulse output operation of the optical output in the long pulse and short pulse output operation modes is started based on the change amount of the optical output in the long pulse and short pulse output operation modes. A semiconductor laser deterioration determination that determines the rate of change from time and determines the deterioration state of the laser diode from the rate of change and the previously stored data relating to the characteristics of the laser diode and outputs the determination result to the outside. It is equipped with means.

[0017]

According to the present invention, the change amount of the laser light output of the laser diode in the long pulse output operation mode having a large pulse width among the plurality of pulse output operation modes is monitored, and the monitored change amount of the laser light output, Estimating the amount of change in the laser light output of the laser diode in the short pulse output operation mode with a small pulse width among the plurality of pulse output operation modes from the previously stored data relating to the characteristics of the laser diode, the short pulse output In the operation mode, constant current control is performed so that the current for driving the laser diode becomes a drive current in which the estimated change amount of the laser light output is corrected, and the light in the short pulse output operation mode of the laser diode is operated. Since the output is kept constant, a semiconductor having an element with an expensive high-speed response Without using a chromatography The driving device,
The optical output of a short pulse having a pulse width of, for example, the order of μsec, can be accurately kept constant.

Further, in the present invention, during the long pulse output operation, constant light output control is performed so that the current for driving the laser diode becomes a drive current corrected for the amount of change in the monitored laser light output. Since the light output of the laser diode in the long pulse output operation mode is kept constant, the light outputs of long pulses other than short pulses can be kept constant with high precision.

Further, in the present invention, the change amount of the laser light output of the laser diode in the long pulse output operation mode having a large pulse width among the plurality of pulse output operation modes is monitored, and the change amount of the monitored laser light output is monitored. From the previously stored data relating to the characteristics of the laser diode, the change amount of the laser light output of the laser diode in the short pulse output operation mode with a small pulse width among the plurality of pulse output operation modes is estimated, and the length is calculated. From the change amount of the light output in the pulse and short pulse output operation modes, the change rate of the light output in the long pulse and short pulse output operation modes from the start of the pulse output operation is obtained, and the change rate and the From the stored data on the characteristics of the laser diode, the deterioration state of the laser diode Determined, it is so arranged to output the determination result to the outside, it is possible to determine the deterioration of the characteristics of the laser diode even when the pulse width is for example to perform the pulse output operation including a short pulse of μsec order.

Further, according to the present invention, the monitor means for monitoring the change amount of the laser light output of the laser diode in the long pulse output operation mode having a large pulse width among the plurality of pulse output operation modes, and the monitored laser light output. Of the laser diode output from the plurality of pulse output operation modes having a small pulse width among the plurality of pulse output operation modes. In the change amount estimating means and the short pulse output operation mode, constant current control is performed so that the current for driving the laser diode becomes a drive current corrected for the estimated change amount of the laser light output, and the laser diode is operated. And a constant current control means for making the light output constant in the short pulse output operation mode. Takara, without using the semiconductor laser drive device having an element with an expensive high-speed response,
The optical output of a short pulse having a pulse width of, for example, the order of μsec, can be accurately kept constant.

Further, in the present invention, during the long pulse output operation, constant light output control is performed so that the current for driving the laser diode becomes a drive current corrected for the amount of change in the monitored laser light output. Since the constant light output control means for making the light output of the laser diode in the long pulse output operation mode constant is provided, the light outputs of long pulses other than short pulses can also be kept constant with high precision.

According to the present invention, in the semiconductor laser driving device, the long pulse, the long pulse, and the short pulse are calculated from the change amount of the optical output in the long pulse and short pulse output operation modes.
And the change rate of the light output in the short pulse output operation mode from the start of the pulse output operation, and the deterioration state of the laser diode is determined from the change rate and the data on the characteristics of the laser diode stored in advance. Since the semiconductor laser deterioration judging means for judging and outputting the judgment result to the outside is provided, it is possible to judge the deterioration of the characteristics of the laser diode even when performing a pulse output operation including a short pulse having a pulse width of, for example, μsec. it can.

[0023]

【Example】

Example 1. 1 is a diagram for explaining a semiconductor laser driving method according to a first embodiment of the present invention, and is a diagram schematically showing the configuration of a semiconductor laser driving device. The semiconductor laser driving method of this embodiment is applied to laser driving including a plurality of pulse output operation modes including a short pulse output operation mode. In the figure, 1 is a laser diode,
2 is a photodiode for monitoring, 3 is a laser diode drive circuit for supplying a drive current to the laser diode 1,
Reference numeral 4 is a constant light output control (auto power control) circuit (hereinafter, referred to as APC circuit) for keeping the laser light output constant, and 5 is a constant current control circuit (hereinafter, ACC circuit) for controlling the drive current to a constant current. 6) is an ACC circuit 5
The ACC control circuit 6 controls the relationship between the optical output P of the laser diode 1 and the drive current I (hereinafter referred to as PI characteristic) for each operation mode having different pulse widths. The measured data or the simulation value of the data relating to the operating characteristics of the laser diode 1, such as the data relating to the PI characteristics of the operating temperature of the laser diode 1 and the like, is stored, and the change in the optical output of the long pulse is stored. When a signal indicating the amount is input, the change amount of the optical output of the short pulse is estimated based on the above data, and the optical output during the short pulse output operation becomes the value before the change based on the estimated value. A signal for correcting the drive current value controlled by the ACC circuit 5 is output to the ACC circuit 5. 7 is an APC circuit 4 and an ACC circuit 5
And a connection switch for turning on / off the connection between the APC circuit 4 and the ACC control circuit 6, and a pulse signal for switching the pulse output operation mode of the laser diode 1. The drive control circuit 9 sends the laser diode drive circuit 3 to the laser diode drive circuit 3 at a predetermined timing according to the pulse width of
Although not shown, the changeover switch 7 and the connection switch 8
The switch 7 and the connection switch 8 are switched according to the switching of the operation mode. In this semiconductor laser driving device, the laser diode 1
Has its input side connected to the laser diode drive circuit 3, the photodiode 2 is arranged so as to monitor the emitted light of the laser diode 1, and the output of the photodiode 2 is connected to the APC circuit 4.
One of the outputs of the circuit 4 is connected to the ACC control circuit 6 via the switch 8 and the other is connected to the laser diode drive circuit 3 via the switch 7, and the ACC control circuit 6
Is connected to the ACC circuit 5, the output of the ACC circuit 5 is connected to the laser diode drive circuit 3 via the switch 7, and the output of the drive control circuit 9 is connected to the laser diode drive circuit 3.

FIG. 2 is a diagram showing an optical output waveform of a pulse output from the laser diode 1 by the semiconductor laser driving method of the present invention (FIG. 2 (a)), and a laser diode drive for obtaining the optical output. FIG. 3 is a diagram showing a drive current waveform output from the circuit 3 (FIG. 2B) and a diagram showing a change over time of the drive current in the long pulse output operation mode (FIG. 2C). In Fig. 2 (a), the vertical axis shows the optical output and the horizontal axis shows the time. In Fig. 2 (b), the vertical axis shows the driving current and the horizontal axis shows the time, and in Fig. 2 (c). The vertical axis is the drive current,
The horizontal axis represents time. In the figure, a is the pulse width t
a is a short pulse of the order of μsec, b is a pulse width tb wider than the short pulse a, for example, the pulse width tb is mse.
A long pulse of c order, 11 is a normal drive current for driving the laser diode 1, and 12 is a drive current in a state where the laser characteristics of the laser diode 1 are deteriorated. Further, P2 is an optical output of a short pulse a, P1 is an optical output of a long pulse b, and I2 and I1 are driving for obtaining an optical output P2 of a short pulse a and an optical output P1 of a long pulse b at a driving current 11. Current, I'2 and I'1 are drive currents 12
The drive current for obtaining the light output P2 of the short pulse a and the light output P1 of the long pulse b in Δ, and ΔI1 indicate the increment of the drive current for keeping the light output constant.

FIG. 3 is a diagram showing the operating characteristics of the laser diode 1 driven by the semiconductor laser driving method of this embodiment. FIG. 3 (a) is a pulse output operation mode, laser light output, and drive current. Fig. 3 (b) shows the relationship between the operating temperature, the laser light output, and the operating current (P-I characteristic) during the long pulse output operation of the laser diode 1. There is. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.
Indicates the PI characteristics of the short pulse a and the long pulse b, respectively, and 22 and 23 indicate the long pulse b at low temperature,
And P-I characteristics at high temperature, I1 (l), I1 (h) are
The drive current required to obtain the optical output P1 at low temperature and high temperature is shown. Further, ΔI1 indicates the amount of increase in the drive current for keeping the optical output constant.

Next, a description will be given of a case where the semiconductor laser control method of this embodiment is used to perform a pulse output operation having two output operation modes of a short pulse a and a long pulse b as shown in FIG. 2 (a). To do. First, from the drive control circuit 9,
When a signal is sent to the laser diode drive circuit 3 at a timing matched with the pulse widths ta and tb of the short pulse a and the long pulse b, the laser diode drive circuit 3 sends a signal to the laser diode 1 as shown in FIG. The normal drive current 11 as shown in (1) is repeatedly output at a predetermined interval. This drive current 11 causes a short pulse a and a long pulse b.
And are output while sandwiching a predetermined non-driving period.

Here, when the short pulse a is output,
The connection switch 8 is turned off by the signal output from the drive control circuit 9, the laser diode drive circuit 3 and the ACC circuit 5 are connected by the changeover switch 7, and the ACC circuit 5 keeps the drive current of the laser diode 1 constant. The laser diode drive circuit 3 is subjected to constant current control by outputting a signal to the laser diode drive circuit 3, and the laser diode drive circuit 3 drives the laser diode 1 with a constant drive current I2.

Next, when the long pulse b is output, the changeover switch 7 is controlled by the signal output from the drive control circuit 9 so that the APC circuit 4 and the laser diode drive circuit 3 are connected, and the laser diode The laser light emitted from 1 is received by the photodiode 2, and the signal output from this photodiode 2 is input to the APC circuit 4. At this time, if the optical output of the laser diode 1 is reduced due to element heat generation or deterioration of the element over time, and the input value from the photodiode 2 to the APC circuit 4 is reduced, the long pulse b from the APC circuit 4 is reduced. A signal for correcting the optical output of the laser diode 1 to the same value as the original optical output is sent to the laser diode drive circuit 3, and this signal causes the optical output of the long pulse b to deteriorate before the laser diode 1 deteriorates. The laser diode drive circuit 3 outputs a drive current I′1 having the same value as the optical output of the laser diode. In this way, the long pulse b is controlled by the photodiode 2 and the APC circuit 4 for a change in light output, and the monitored result is fed back to the laser diode drive circuit 3 to control the constant light output. The output is kept constant. The change in the P-I characteristic due to the change in operating temperature of the long pulse b is as shown in FIG. 3 (b), and when the operating temperature changes from low temperature to high temperature due to heat generation, the same output P1 is obtained. It can be seen that it is necessary to change the drive current from I '(l) to I' (h). Also,
The change of the drive current of this long pulse b with time becomes as shown in FIG. 2 (c). When the drive time becomes long, it is necessary to increase the drive current by ΔI1 in order to obtain a constant light output. I understand.

Here, when the long pulse b is output, the switch 8 is also turned on by the drive control circuit 9, and the APC circuit 4 and the ACC control circuit 6 are connected.
When the operation characteristics of the laser diode 1 in the long pulse b output operation mode change, a signal indicating the amount of change in the output from the photodiode 2 during the long pulse b output is input to the ACC control circuit 6 from the APC circuit 4. To be done. This AC
As described above, the C control circuit 6 internally has data regarding the P-I characteristics of the short pulse a and the long pulse b of the laser diode 1 as shown in FIGS. 3 (a) and 3 (b), and Data relating to the laser characteristics of the laser diode 1 as shown in FIGS. 3 (a) and 3 (b), such as data relating to the relationship between the driving temperature of the long pulse and the PI characteristics, are stored in advance. When the data of the amount of change in the optical output of the laser diode 1 at the time of outputting the long pulse b is input to the ACC control circuit 6, the data from the APC circuit 4 is compared with the data of the laser characteristic, and the laser diode is compared. The drive state of No. 1 is detected, the change amount of the optical output at the time of short pulse a output is estimated based on these data, the change amount of the optical output is corrected, and the optical output before the change is determined by the laser. Driving power required to obtain from diode 1 The flow I'2 is calculated and a signal for causing the laser diode drive circuit 3 to output the drive current I'2 is sent to the ACC circuit 5. A upon receiving this signal
The CC circuit 5 can perform constant current control of the laser diode drive circuit 3 so that the drive current output from the drive circuit 3 becomes a value I′2 corrected in accordance with the change amount of the optical output. It will be possible.

Then, after the long pulse b is output as described above, a signal for stopping the driving of the laser diode 1 is sent from the drive control circuit 9 to the laser diode driving circuit 3 so that the laser diode 1 is not driven. At the same time, turn off the connection switch 8 and set the changeover switch 7 to A
When neither the PC circuit 4 nor the ACC circuit 5 is connected to the drive control circuit 9, the optical output is monitored by the photodiode 2 and the drive current is controlled by the APC circuit 4, the ACC circuit 5, and the ACC control circuit 6. The non-driving period of the laser diode 1 is provided between the short pulse and the long pulse.

Next, the switch 7 is switched in the same manner as described above to connect the ACC circuit 5 and the laser diode drive circuit 3 and output a short pulse a. At this time, as described above,
The ACC circuit 5 is controlled by the signal from the ACC control circuit 6 so as to perform constant current control with the drive current I′2 in which the amount of change in optical output is corrected as the drive current in the short pulse a output operation mode. The short pulse a has the same optical output as the optical output P2 before the optical output changes due to the drive current I′2. After that, the long pulse output operation mode, the non-driving period, and the short pulse output operation mode are sequentially repeated while performing the same control as above.

In the present embodiment, in the long pulse b output operation mode, the optical output of the laser diode 1 is controlled by the APC circuit 4 in the same manner as in the conventional case, and the laser diode 1 monitored at the output of the long pulse b is output. The amount of change in the optical output of the laser diode 1 is input to the ACC control circuit 6 that stores data relating to the operating characteristics of the laser diode 1,
The CC control circuit 6 estimates the amount of change in the operating characteristics of the laser diode 1 at the time of outputting a short pulse a based on the above data, and obtains the drive current I′2 necessary to compensate for the amount of change in the optical output. The laser diode drive circuit 3 is controlled by using the ACC circuit 5 so that the drive current I′2 corrected for the deterioration of the optical output is output from the laser diode drive circuit 3.
Is controlled by a constant current so as to keep the optical output of the short pulse a constant even when the operating characteristics of the laser diode 1 are deteriorated. The optical output in the short short pulse output operation mode is monitored and the long pulse b having a relatively long pulse width is maintained based on the change amount of the optical output without using the APC circuit to keep the optical output constant. Since it is possible to monitor and perform constant current control of the optical output of the short pulse a on the basis of the change amount of the optical output of the long pulse b, it is possible to use a monitor photodiode having a high-speed response which is expensive and a high-speed response. The optical output of the short pulse a can be controlled without using an APC circuit equipped with a responsive element, and a highly accurate pulse can be obtained at low cost. Further, even when the pulse width of the short pulse is very short and it is difficult to monitor and feedback the pulse by the photodiode 2 or the APC circuit 4, it is possible to monitor the change in the optical output of the long pulse having the monitorable pulse width. Since it is possible to estimate the decrease in the optical output in the short pulse output operation mode, it is possible to stably output an accurate pulse.

As described above, according to this embodiment, the short pulse a
In a semiconductor laser driving method having an output operation mode and a long pulse b output operation mode, the change amount of the optical output of the short pulse a is based on the change amount of the optical output obtained by monitoring the long pulse b. , The laser diode drive circuit 3 in the short pulse a output operation mode is estimated by the drive current I′2 that is estimated by using the data regarding the operating characteristics of the laser diode 1 and the optical output obtained by correcting the amount of change in the optical output is obtained. In addition to the constant current control, the long pulse output operation mode is further controlled by the constant light output using the APC circuit 4. Therefore, the monitor photodiode having high-speed response, which is expensive, and the high-speed response are provided. A pulse width of μsec is obtained by using an inexpensive semiconductor laser driving device without using a semiconductor laser driving device having an APC circuit including an element.
There is an effect that the optical output of the short pulse and the long pulse of the order can be accurately kept constant and stably output.

In the first embodiment, the semiconductor laser driving method provided with the two operation modes of the short pulse output operation mode and the long pulse output operation mode has been described, but the present invention is as shown in FIG. It is also applicable to a plurality of pulse output operation modes including a short pulse output operation mode, and a semiconductor laser driving method including a non-driving period. In such a case, the optical output of the pulse with the longest pulse width is obtained. , For example, in FIG. 4, pulse d
The amount of change in the optical output obtained by monitoring the optical output of
Input to the control circuit, estimate the amount of change in the optical output of other short pulses c and e with reference to this, and correct the optical output in the short pulse output operation mode based on this amount of change. Even in such a case, the same effect as that of the above-described embodiment can be obtained. In FIG. 4, c and e are short pulses, and d is a pulse having the longest pulse width.
P3, P4, and P5 indicate the optical outputs of the pulses d, e, and c, respectively.

Example 2. FIG. 5 is a block diagram schematically showing a structure of a semiconductor laser driving device for explaining a semiconductor laser deterioration judging method according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. A corresponding portion is shown, and 10 is a detection circuit for determining deterioration of the laser diode 1.

Usually, the laser diode deteriorates with the passage of time, the original operating characteristics are completely lost, and the original optical output cannot be obtained even if the drive current is controlled. In a semiconductor laser driving device used in a system that requires high reliability, such as an optical disk memory device that records highly accurate information for a long period of time, an element is required before the semiconductor laser is in such a completely deteriorated state. Must be replaced to prevent system down and improve system reliability. The present invention provides the semiconductor laser driving method according to the first embodiment, wherein the operating characteristics of the laser diode are completely deteriorated before
The deterioration of the laser diode is judged and the complete deterioration of the laser diode can be warned.

Next, the deterioration determination method of this embodiment will be described. The semiconductor laser driving device of the present embodiment is driven in a plurality of pulse output operation modes including a short pulse output operation mode having a pulse width of the order of μsec by a method similar to the method of driving the semiconductor laser of the first embodiment. . Here, as in the first embodiment, the optical output of the laser diode 1 is received by the photodiode 2 and converted into a signal, which is input to the APC circuit 4 and is passed through the switch 8 to the ACC.
When input to the control circuit 6, data indicating the amount of change in optical output of the laser diode 1 input to the ACC control circuit 6 in other long pulse operation modes, and the ACC control circuit 6
According to the above, the data of the variation amount of the optical output in the short pulse output operation mode in which the pulse width estimated from the variation amount of the optical output in the long pulse operation mode is in the order of μsec is obtained.
Input to 0. Here, in advance, the detection circuit 10 is made to store data relating to the change rate of the operating characteristics of the laser diode 1 over time, such as the deterioration of the optical output over time, and the detection circuit 10 uses the above ACC control circuit 6 The change rate of the optical output from the start of the pulse output operation of the short pulse and the long pulse is obtained on the basis of the data input from, and the change rate in the detection circuit 10 and the stored data are obtained. By comparison, the deterioration state of the laser diode 1 is determined, and if it is determined that the laser diode 1 is in a state immediately before the original operating characteristics are completely lost, the detection circuit 10 causes the alarm LED ( An alarm (not shown) is turned on or a beep sound is output to the outside to notify the laser diode 1 of the replacement time.

As described above, in the present embodiment, the short pulse output and other parameters are obtained by using the change amount of the optical output between the short pulse a output operation mode and the other long pulse output operation modes obtained in the first embodiment. The change rate of the long pulse output from the start of the pulse output operation is obtained, and the deterioration state is determined by comparing this with the data regarding the temporal characteristics of the laser diode 1 prepared in advance. Provide a highly reliable semiconductor laser deterioration determination method capable of determining deterioration of a laser diode even in a semiconductor laser driving method having a plurality of pulse output operation modes including a short pulse output operation mode of μsec order. This makes it possible to perform maintenance such as maintenance and replacement of the laser diode before the system goes down. Come, it is possible to improve the reliability of the system.

[0039]

According to the present invention, the change amount of the laser light output of the laser diode in the long pulse output operation mode having a large pulse width among a plurality of pulse output operation modes is monitored, and the change amount of the monitored laser light output is monitored. From the previously stored data relating to the characteristics of the laser diode, the amount of change in the laser light output of the laser diode in the short pulse output operation mode with a small pulse width among the plurality of pulse output operation modes is estimated, and the short In the pulse output operation mode, constant current control is performed so that the current for driving the laser diode becomes a drive current corrected for the estimated change amount of the laser light output, and in the short pulse output operation mode of the laser diode. Since it keeps the optical output of the device constant, it has an expensive element with high-speed response. A semiconductor laser driving method capable of stably outputting a short pulse having a pulse width of, for example, the order of μsec, accurately and stably without using a conductor laser driving device and using a cheap semiconductor laser driving device. There is an effect that can be provided.

Further, in the present invention, constant light output control is performed so that the current for driving the laser diode becomes a drive current in which the amount of change in the monitored laser light output is corrected during the long pulse output operation. Since the optical output of the laser diode in the long pulse output operation mode is kept constant, a semiconductor laser capable of accurately keeping the optical output of a long pulse other than a short pulse constant There is an effect that a driving method can be provided.

Further, in the present invention, the change amount of the laser light output of the laser diode in the long pulse output operation mode having a large pulse width among the plurality of pulse output operation modes is monitored, and the change amount of the monitored laser light output is monitored. From the previously stored data relating to the characteristics of the laser diode, the change amount of the laser light output of the laser diode in the short pulse output operation mode with a small pulse width among the plurality of pulse output operation modes is estimated, and the length is calculated. From the change amount of the light output in the pulse and short pulse output operation modes, the change rate of the light output in the long pulse and short pulse output operation modes from the start of the pulse output operation is obtained, and the change rate and the From the stored data on the characteristics of the laser diode, the deterioration state of the laser diode Since the determination result is output to the outside, the deterioration of the characteristics of the laser diode can be determined even in the short pulse output operation with the pulse width of, for example, μsec order, and the highly reliable semiconductor laser deterioration determination can be performed. There is an effect that can provide a method.

Further, in the present invention, the monitor means for monitoring the change amount of the laser light output of the laser diode in the long pulse output operation mode having a large pulse width among the plurality of pulse output operation modes, and the monitored laser light output. Of the laser diode output from the plurality of pulse output operation modes having a small pulse width among the plurality of pulse output operation modes. In the change amount estimating means and the short pulse output operation mode, constant current control is performed so that the current for driving the laser diode becomes a drive current corrected for the estimated change amount of the laser light output, and the laser diode is operated. And a constant current control means for making the light output constant in the short pulse output operation mode. Takara, pulse width, for example μsec
A short-time pulse of the order, a semiconductor laser driving device that can stably output a stable light output with high precision, without using an expensive high-speed responsive element,
There is an effect that it can be provided at low cost.

Further, in the present invention, during the long pulse output operation, constant light output control is performed so that the current for driving the laser diode becomes a drive current in which the amount of change in the monitored laser light output is corrected. Since the laser diode is provided with a constant light output control means for making the light output constant in the long pulse output operation mode, it is possible to stably and stably output the light output with a high precision even for long pulses other than short pulses. There is an effect that a semiconductor laser driving device that can be provided can be provided at low cost.

According to the present invention, in the semiconductor laser driving device, the long pulse, the long pulse, and the long pulse are calculated from the change amount of the optical output in the long pulse and short pulse output operation modes.
And the change rate of the light output in the short pulse output operation mode from the start of the pulse output operation, and the deterioration state of the laser diode is determined from the change rate and the data on the characteristics of the laser diode stored in advance. Since the semiconductor laser deterioration judging means for judging and outputting the judgment result to the outside is provided, it is possible to judge the deterioration of the characteristics of the laser diode even in the short pulse output operation with a pulse width of, for example, the order of μsec, which is highly reliable. The semiconductor laser driving device can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing the structure of a semiconductor laser driving device according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a pulse obtained by the semiconductor laser driving method according to the first embodiment of the present invention.

FIG. 3 is a diagram showing operating characteristics of a laser diode used in the semiconductor laser driving method according to the first embodiment of the present invention.

FIG. 4 is a diagram schematically showing a pulse obtained by a semiconductor laser driving method according to a modification of the first embodiment of the present invention.

FIG. 5 is a block diagram showing a structure of a semiconductor laser driving device according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a structure of a conventional semiconductor laser driving device.

FIG. 7 is a diagram schematically showing a pulse obtained by a conventional semiconductor laser driving method.

[Explanation of symbols]

1 laser diode, 2 photo diode, 3 laser diode drive circuit, 4 APC circuit, 5 ACC
Circuit, 6 ACC control circuit, 7 changeover switch, 8
Connection switch, 9 Drive control circuit, 10 Detector, 11
Normal drive current, 12 drive current when laser characteristics deteriorate, 20 short pulse PI characteristics, 21 long pulse P-
I characteristic, 22 P-I characteristic at low temperature, 23 P at high temperature
-I characteristic.

Claims (6)

[Claims] 1. A method of driving a laser diode in a plurality of pulse output operation modes having different pulse widths, wherein a laser light output of the laser diode in a long pulse output operation mode having a large pulse width among the plurality of pulse output operation modes. In the short pulse output operation mode with a small pulse width among the plurality of pulse output operation modes, based on the monitored change amount of the laser light output and the previously stored data relating to the characteristics of the laser diode. The change amount of the laser light output of the laser diode is estimated, and in the short pulse output operation mode, the current for driving the laser diode is set to be a drive current corrected by the estimated change amount of the laser light output. By controlling the current, the short pulse output operation mode of the laser diode A method for driving a semiconductor laser, characterized in that the light output is kept constant. 2. The semiconductor laser driving method according to claim 1, wherein the current for driving the laser diode during the long pulse output operation is a driving current corrected for the amount of change in the monitored laser light output. The semiconductor laser driving method is characterized in that the constant light output control is performed to make the light output of the laser diode in the long pulse output operation mode constant. 3. A method for determining deterioration of a laser diode driven in a plurality of pulse output operation modes having different pulse widths, wherein the laser is used in a long pulse output operation mode having a large pulse width among the plurality of pulse output operation modes. The amount of change in the laser light output of the diode is monitored, and based on the monitored amount of change in the laser light output and the previously stored data relating to the characteristics of the laser diode, a short pulse having a small pulse width among the plurality of pulse output operation modes is selected. The amount of change in the laser light output of the laser diode in the pulse output operation mode is estimated, and from the amount of change in the optical output in the long pulse and short pulse output operation modes, the light in the long pulse and short pulse output operation modes is calculated. The change rate of the output from the start of the pulse output operation is calculated, and the change rate is stored in advance. A method for determining deterioration of a semiconductor laser, characterized in that the deterioration state of the laser diode is judged from the data relating to the characteristics of the laser diode, and the judgment result is output to the outside. 4. A semiconductor laser drive device for driving a laser diode in a plurality of pulse output operation modes having different pulse widths, wherein the laser diode in a long pulse output operation mode having a large pulse width among the plurality of pulse output operation modes is used. Based on the monitoring means for monitoring the change amount of the laser light output, the monitored change amount of the laser light output, and the previously stored data relating to the characteristics of the laser diode, the pulse width of the plurality of pulse output operation modes is the smallest. A change amount estimating means for estimating a change amount of the laser light output of the laser diode in the short pulse output operation mode, and a change amount of the estimated laser light output by the current for driving the laser diode in the short pulse output operation mode. The constant current is controlled so that the drive current is corrected for A semiconductor laser driving device, comprising: a constant current control means for making constant the light output of the laser diode in the short pulse output operation mode. 5. The semiconductor laser drive device according to claim 4, wherein the current for driving the laser diode during the long pulse output operation is a drive current corrected for the amount of change in the monitored laser light output. A semiconductor laser drive device comprising constant light output control means for controlling the constant light output as described above to make the light output of the laser diode in the long pulse output operation mode constant. 6. The semiconductor laser driving device according to claim 4, wherein the light output in the long pulse and short pulse output operation modes is changed from the change amount of the light output in the long pulse and short pulse output operation modes. , The rate of change from the start of the pulse output operation is obtained, and the deterioration state of the laser diode is determined from the rate of change and the previously stored data relating to the characteristics of the laser diode, and the determination result is output to the outside. A semiconductor laser driving device, comprising: