JPH0714098B2 - Laser output controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser output control device, and more particularly to a control device for maintaining a constant laser output during processing.

2. Description of the Related Art Conventionally, there has been a device of this type shown in FIG.
In the figure, a half mirror B is provided on the optical axis of the laser beam from the laser oscillator A, and a part of the laser beam is transmitted by the half mirror B and the rest is reflected and guided to the workpiece W. Behind the half mirror B, an output power detector C for detecting a laser output by a part of the transmitted laser light is provided. The output of the output power detector C is amplified by the amplifier D and input to the comparator E. In the comparator E, the amplified output power value is compared with the command power value from the output setting device F, and the error signal is amplified by the error amplifier G and given to the current control circuit H to output the output power of the laser oscillator A. Feedback control was performed to match the command power.

However, in this method, the laser light once emitted from the laser oscillator A is reflected by the workpiece W, and the reflected light re-enters the laser oscillator A along the reverse path and is mixed with the laser light, so that the output power is detected. Since the reflected light is also detected in the container C at the same time, the laser output becomes as shown in FIG. 3, and the actual output excluding the reflected light decreases. Therefore,
The laser output during non-processing when the shutter I is closed is stable, but the detected output changes irregularly due to the addition of reflected light components during processing when the shutter I is open, and the reflected light components are The actual effective output, which was removed, decreased and changed irregularly as shown by the wavy shape in FIG. 3, and there was a defect that good processing was difficult.

Object of the Invention and Solution Therefor It is an object of the present invention to eliminate the influence of reflected light components on the output power and to always maintain a stable laser output.

Therefore, in the present invention, a reflection power detector is provided in addition to the output power detector to detect the reflection power, and the value obtained by subtracting the value of the reflection power detector from the value of the output power detector and the required laser output power The output is controlled by comparing the difference with the value and feeding back the difference to the laser oscillator.

Configuration of the Invention Hereinafter, a specific configuration of the present invention will be described with reference to FIG.

Reference numeral 1 denotes a laser oscillator which forms a discharge part 4 between an anode 2 and a cathode 3 and outputs a laser beam from the discharge part 4. The laser oscillator 1 is provided to face each other via the discharge part 4. Total reflection mirror 5 and output half mirror 6
have. Reference numeral 7 is a power supply for supplying a voltage between the anode 2 and the cathode 3 of the laser oscillator 1, and 8 is a current control circuit for controlling the current to the laser oscillator 1. Further, 9 is a half mirror provided on the optical axis of the laser light extracted from the half mirror 6 of the laser oscillator 1, and this half mirror 9 transmits a part of the laser from the laser oscillator 1 and All of them are reflected in a right angle direction and guided onto the workpiece W as a processing laser. Reference numeral 10 is an output power detector provided on the opposite side of the laser oscillator 1 via the half mirror 9 for detecting a laser output by a beam transmitted through the half mirror 9, and 11 is a workpiece to be processed via the half mirror 9. The reflection power detector is provided on the side opposite to the object W and detects the reflected light reflected by the workpiece W by the transmitted light of the half mirror 9. 12 is a first amplifier that amplifies the detection signal from the output power detector 10 to a required level, 13 is a second amplifier that amplifies the detection signal from the reflection power detector 11 to a required level, and 14 is an NC tape or the like. It is a power setting means for designating the output power of the laser. Reference numeral 15 is a comparator, which has the input from the first amplifier 12 as a negative pole, the second amplifier 13 and the power setting means 14
From the output power value minus the reflected power value and the command power value from the setting means 14 are compared, and the difference is sent as an error signal to the error amplifier 16 in the next stage. . Then, the output of the error amplifier 16 is sent to the current control circuit 8 to form a series of feedback systems.

Operation of the Invention Next, the operation of the present apparatus will be described.

First, when a voltage is applied from the power supply 7 between the anode 2 and the cathode 3 of the laser oscillator 1, the discharge portion 4 is formed, and laser light is generated between the facing total reflection mirror 5 and the half mirror 6.
It is emitted to the outside through the half mirror 6. A part of the laser light output from the laser oscillator 1 passes through the half mirror 9 and is used as a detection laser light to output power detector 10
Is incident on the workpiece W, and the other light is reflected by the half mirror 9 and emitted toward the workpiece W as processing laser light. When reflected light is generated by the workpiece W during the processing in which the shutter 17 is opened, the reflected light follows a path opposite to the laser irradiation direction, and part of the reflected light passes through the half mirror 9 in the middle and is reflected backward. The light is incident on the power detector 11 as reflected power detection light, and the other light is reflected by the half mirror 9 to be re-incident on the laser oscillator 1, reflected by the total reflection mirror 5 and the half mirror 6, and mixed in the laser light. Therefore, the output power detector
At 10, irregular power with reflected light component is detected. The output of the output power detector 10 is amplified to a required level by the first amplifier 12 and input to the comparator 15 with a negative polarity. At the same time, the output of the reflected power detector 11 is input to the comparator 15 amplified by the second amplifier 13 to a required level with a positive polarity. Further, the command power value from the power setting means 14 is input to the comparator 15 with a positive polarity. Therefore, the comparator 15 compares the detected power value with the command power value and In order to correct the decrease, the error value is corrected by the amount of the reflected power. That is, the value obtained by subtracting the reflected power value from the detected power value is compared with the command power value, and the error signal is amplified by the error amplifier 16 and sent to the current control circuit 8. In this way, a series of output compensation control systems is configured to maintain a stable actual laser output as indicated by the dotted line in FIG.

As described above, the present invention provides an output compensation control system for keeping the output power constant, in addition to the output power detector, a reflection power detector for detecting reflected light reflected by the workpiece. A value obtained by removing the power value of the reflected power detector from the power value of the output power detector is compared with the command power value, and the laser output is compensated and controlled by the error, so that the reflected light depends on the workpiece. Even if the reflected light re-enters the laser oscillator and mixes into the laser light, the reflected light component is removed from the output power value to which the reflected light component is added, and the actual output power is stabilized according to the command power. Can be held at. Therefore, even if the reflected light is generated, there is an effect that the output power does not change and stable processing can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a device of the present invention, FIG. 2 is a diagram showing a conventional device, and FIG. 3 is a diagram for explaining defects of the conventional device. 1 ... Laser oscillator, 8 ... Current control circuit, 9 ... Half mirror, 10 ... Output power detector, 11 ... Reflection power detector, 14
… Power setting means, 15… Comparator, W… Workpiece.

Claims (1)

[Claims] 1. A laser oscillator, a current control circuit for controlling a current to the laser oscillator, and a part of laser light output from the laser oscillator, which is provided on the optical axis of the laser light from the laser oscillator. And a half mirror that reflects the other in a direction perpendicular to the workpiece, an output power detector that detects the laser output of the laser light that has passed through this half mirror, and a workpiece from the workpiece through the half mirror. A reflected power detector for detecting reflected light, an output power setting means for instructing a laser output, a value obtained by removing the power value of the reflected power detector from the power value of the output power detector, and the output power setting means. And a comparator for giving a current value proportional to the difference between the command power value and the command power value.