JPH0513554B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor laser output control device, and in particular detects a laser output level and controls the drive of a semiconductor laser using a difference signal between this level and a reference voltage. The present invention relates to a semiconductor laser output control device that controls the level of laser output to a constant value.

[Conventional technology]

Conventionally, this type of semiconductor laser output control device is
As shown in FIG. 2, a laser output detection section 4 such as a photodiode that detects the laser output of the semiconductor laser 7, a level detection section 5 that detects the level of the output signal of the laser output detection section 4, and a level detection section 5 that detects the level of the output signal of the laser output detection section 4; Compare the output signal of section 5 with a set voltage Vs for setting the laser output level to a predetermined value,
It is equipped with a comparison section 2 that outputs a difference signal, and a laser drive section 3 that drives and controls the semiconductor laser 7 using this difference signal, and is configured to perform additional value control so that the difference signal becomes zero, and is capable of level detection. Part 5 is usually
It consists of a circuit including a capacitor and a resistor, and the peak value is detected by the charging voltage of this capacitor.

[Problem that the invention seeks to solve]

The conventional semiconductor laser output control device described above is
Since the level detection unit 5 that detects the level of the laser output is configured to detect the charging voltage of the capacitor, it is normally controlled when the laser output is a continuous wave, but when the laser output is pulse modulated, etc. If the output is intermittent, the level detection unit 5
Since the output level changes depending on the pulse width and the true value cannot be detected, the laser output changes depending on the pulse width, and it is difficult to set the laser output to the desired level.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser output control device that prevents the laser output from changing depending on the pulse width and allows easy setting of the laser output level.

[Means for solving problems]

The semiconductor laser output control device of the present invention includes a laser output detection section that detects the laser output of the semiconductor laser, a level detection section that detects the level of the output signal of the laser output detection section, and an output signal of the laser output detection section. a pulse width detection unit that detects the pulse width of the laser output from the pulse width detection unit; and a reference voltage generation unit that generates a reference voltage by synthesizing the output voltage of the pulse width detection unit and a set voltage for setting the level of the laser output. and a comparison section that compares the reference voltage and the output signal of the level detection section and outputs a difference signal;
and a laser driving section that drives the semiconductor laser using the difference signal and controls the laser output to a predetermined level.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

A portion of the laser output emitted from the semiconductor laser 7 is detected by a laser output detection section 4 such as a photodiode, and enters a level detection section 5. The level detecting section 5 is a type of integrating circuit composed of a circuit including a capacitor and a resistor, and detects a peak value from the charging voltage of this capacitor and outputs it to the comparing section 2.

On the other hand, the output signal of the laser output detection section 4 is also transmitted to the pulse width detection section 6, which similarly outputs a voltage corresponding to the pulse width using a kind of integration circuit. The output voltage of the pulse width detection section 6 is synthesized by the reference voltage generation section 1 with a setting voltage Vs for setting the level of the laser output, and outputted as a reference voltage.

The comparator 2 compares this reference voltage with the output signal of the level detector 5 and outputs a difference signal between these signals to the laser driver 3. The laser driving section 3 drives the semiconductor laser 7 using this difference signal and controls the laser output to a predetermined level.

Therefore, when the pulse width becomes shorter, the output voltage of the level detection section 5 decreases according to the pulse width, but at the same time, the output voltage of the pulse width detection section 6 also decreases according to the pulse width, and this output voltage and the set voltage Since the reference voltage, which is a composite voltage with Vs, also decreases according to the pulse width, the comparator 2 compares the output voltage of the level detector 5, which fluctuates with the pulse width, in a corrected form. It is possible to prevent the level of the laser output from the laser 7 from changing with the pulse width.

〔Effect of the invention〕

As explained above, the present invention synthesizes the set voltage and the output voltage corresponding to the pulse width from the pulse width detection section to create a reference voltage, compares this reference voltage with the output signal of the level detection section, By configuring the semiconductor laser to be driven and controlled using the difference signal between these signals, it is possible to prevent the level of the laser output from changing depending on the pulse width and to facilitate the level setting of the laser output.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a block diagram showing an example of a conventional semiconductor laser output control device. 1... Reference voltage generation section, 2... Comparison section, 3...
Laser drive unit, 4... Laser output detection unit, 5...
Level detection section, 6... Pulse width detection section, 7... Semiconductor laser.

Claims (1)

[Claims] 1. A laser output detection section that detects the laser output of a semiconductor laser, a level detection section that detects the level of the output signal of the laser output detection section, and a pulse width of the laser output that is detected from the output signal of the laser output detection section. a reference voltage generating section that generates a reference voltage by synthesizing the output voltage of the pulse width detecting section and a setting voltage for setting the level of the laser output; A semiconductor laser comprising: a comparison section that compares the output signal of the section and outputs a difference signal; and a laser drive section that drives the semiconductor laser using the difference signal and controls the laser output to a predetermined level. Output control device.