JPH11121834A - Laser power monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable laser power monitor, which eliminates the effect of reflection return light which is reflected on the optical axis of a laser beam from a laser work and returns to the work. SOLUTION: A laser power monitor is provided with a beam splitter 11 arranged on the optical axis of a laser beam which is outputted from a laser oscillator 101 toward a work 102, an emitted beam detector 12 for detecting the laser beam which is reflected by this beam splitter 11, and a power indicator 13 for indicating the power of this laser beam. Moreover, a return light detector 22 for detecting one part of reflection return light, which is reflected by the splitter 11 and is reflected on the optical axis from the work 102 and returns to the work 102, is juxtaposed to the splitter 11, and an emitted beam signal detected by the detector 12 is corrected by a reflection return light signal detected by the detector 12 to contrive to give the indication of the power of the output of the oscillator 101.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser power monitor, and more particularly, to a laser power monitor used in conjunction with a laser used for laser processing.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional example. The conventional example shown in FIG. 3 includes a beam splitter 61 that is arranged on the optical axis of a laser beam A output from a laser oscillator 101 toward a workpiece 102 and reflects a part of the laser beam A, and the beam splitter 61. An output light detector 62 for detecting the laser light reflected by the laser light, and an output level of the laser light output from the laser oscillator 101 is calculated and displayed based on the laser light detected by the output light detector 62. And a power indicator 63. Reference numeral 64 denotes an amplifier that amplifies the output signal of the output photodetector 62 described above. Thereby, the power of the laser light from the laser oscillator 101 is relatively well monitored by the power display 63.

Here, reference numeral 65 denotes a fixed optical system for guiding the laser beam A toward a workpiece. This fixed optical system 65
Are a fiber incident lens 65A for taking in the laser light transmitted through the beam splitter 61, an optical fiber 65B for guiding the laser light to a predetermined lowering point, and a laser beam guided by the optical fiber 65B for a predetermined workpiece. And a condenser lens 65 </ b> C that outputs the light toward 102.

Further, as other examples of the laser power monitoring device, there are Japanese Utility Model Laid-Open No. 62-060062 and Japanese Patent Laid-Open No. 59-058885.

[0005] Among them, the laser power monitoring device described in Japanese Utility Model Application Laid-Open No. 62-060062 employs a technique of performing power monitoring using a non-reflective coating plate as a beam splitter.

Further, in the laser power monitoring device described in Japanese Patent Application Laid-Open No. Sho 59-058885, power information proportional to the output is obtained regardless of whether the laser light is not linearly polarized light but is either P-polarized light or S-polarized light. So that you can get
Two beam splitters corresponding to this are used. In the first beam splitter and the second beam splitter, the incident angles to the respective beam splitters are set to be the same, the incident surfaces are set to be orthogonal, and power monitoring is performed by a photodetector via the respective beam splitters. The method is adopted.

[0007]

However, in each of the above-mentioned conventional examples, the reflected light reflected on the optical axis from the workpiece and returning to the laser device is reflected by the output mirror of the laser oscillator and output. There has always been an inherent inconvenience in the configuration that the light is re-output together with the light and further reflected by the beam splitter and mixed with the output light and detected. For this reason, in each of the above-mentioned conventional examples, there is an inconvenience that the power monitor value fluctuates between laser processing and non-processing, even though the laser output is constant.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the disadvantages of the prior art and to eliminate the effects of reflected return light that is reflected back on the optical axis from a laser workpiece, thereby providing a laser power monitor with high precision. It is an object of the present invention to provide a highly reliable laser power monitoring device that can achieve the following.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, a part of the laser light is arranged on the optical axis of the laser light output from the laser oscillator toward the workpiece. A beam splitter that reflects light, an output light detector that detects the laser light reflected by the beam splitter, and a laser light output from the laser oscillator based on the laser light detected by the output light detector. A power indicator for displaying the output level of the beam splitter, wherein the return light detector for detecting a part of the reflected return light from the workpiece reflected by the beam splitter is connected to the beam splitter. Attached to

The output light signal detected by the output light detector is corrected by the reflected light signal detected by the return light detector, and the power of the laser oscillator output is displayed. .

According to the first aspect of the present invention, first, a part of the laser light output from the laser oscillator 101 is reflected by the beam splitter 11 and is monitored by the output light detector 12. The laser light A that has passed through the beam splitter 11 is guided to the workpiece 102 and processes the workpiece 102. At this time, a part of the laser light is reflected from the workpiece 102 and returns to the laser oscillator 101. . Part of the reflected return light B is extracted by the beam splitter 11 and monitored by the return light detector 22.

In this case, the remaining portion of the reflected return light B passes through the beam splitter 11, enters the laser oscillator 101, is reflected again by the laser output reflecting mirror 101A, and is output similarly to the laser output light. The laser beam is reflected by the beam splitter 11 and enters the output photodetector 12, which is a laser power detector, and drifts its output signal. On the other hand, correction is performed such that the signal of the return light detector 22 monitoring the reflected return light B is subtracted from, for example, the monitor signal of the drifted laser output.

[0013] This makes it possible to monitor the laser power accurately and stably without being affected by the reflected return light even during laser processing.

In each of the second to fifth aspects of the present invention, first,
A beam splitter that is arranged on the optical axis of laser light output from a laser oscillator toward a workpiece and reflects a part of the laser light, and an output light detector that detects the laser light reflected by the beam splitter And a power display for displaying the output level of the laser light output from the laser oscillator based on the laser light detected by the output light detector, the laser light reflected by the beam splitter. A return light detector for detecting a part of reflected return light from a workpiece to be processed is provided in addition to the above-described beam splitter.

A photodetector correcting means for receiving the outputs of the output photodetector and the return photodetector and correcting the output of the output photodetector with the output of the return photodetector is provided. The above-described configuration of being provided between each power indicator and the output photodetector is adopted as a common basic configuration. Here, the above-described photodetector correction means may be constituted by a differential amplifier. Further, each output stage of the output light detector and the return light detector may be provided with a coefficient adjuster for individually correcting the output of each detector. Further, the power display may be a digital display.

Therefore, each of the inventions according to the second to fifth aspects functions in the same manner as the invention according to the first aspect, and in particular, since a photodetector correcting means is provided, the monitor of the drifted laser output is performed. The drift component can be reliably and accurately subtracted from the signal. This enables accurate and stable laser power monitoring that is not affected by reflected return light even during laser processing.

As described above, in the present invention, since a part of the reflected return light is detected by the beam splitter, it is possible to measure how much the reflected return light is. Furthermore, by displaying the difference between the signal of the reflected return light and the signal of the power monitor, accurate and stable power monitoring is possible even if there is reflected return light.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. In FIG.
Reference numeral 1 denotes a laser oscillator. This laser oscillator 101
In this embodiment, a YAG laser oscillator that oscillates at a wavelength of 1.06 [μm] is used as in the case of the conventional example shown in FIG.

Reference numeral 11 denotes a beam splitter.
This beam splitter 11 has a wavelength of 1.
A dielectric multilayer coating that reflects about 06% of a YAG laser at about 1% is applied to both sides. The beam splitter 11 is disposed on the optical axis of the laser beam A0 output from the laser oscillator 101 toward the workpiece 102 and has a function of reflecting a part of the laser beam.

The laser beam a reflected by the beam splitter 11 is detected by an output photodetector 12 having a silicon photodiode. The laser light a detected by the output light detector 12 is corrected in a predetermined manner as described later, and is then digitally displayed on the power display 13 as a true output level of the laser oscillator 101. .

The laser light A passing through the beam splitter 11 described above is processed by the fixed optical
2 to process the workpiece 102. here,
The fixed optical system 20 includes the beam splitter 11 described above.
Fiber incident lens 2 that captures transmitted laser light A1
0A, an optical fiber 20B for guiding the laser light to a predetermined descending point, and a condensing lens 20C for outputting the laser light guided by the optical fiber 20B toward a predetermined workpiece 102. Has become.

As the fiber incident lens 20A, a lens having a focal length of 20 [mm] is used.
The optical fiber 20B has a core diameter of 600 [μ
m], NA 0.2, and length 5 [m] are used. And, for example, a work distance of 100 [mm]
Is condensed on the workpiece 102 by the condenser lens 20C, whereby the workpiece is laser-processed.

On the other hand, the beam splitter 11 is provided with a return light detector 22 for detecting a part of the return light reflected from the workpiece 102 described above. In the present embodiment, the output light signal detected by the output light detector 12 is corrected by the reflected return light signal detected by the return light detector 22 (actually, the difference is calculated). ), And the power is displayed on the power display 13.

This will be described in more detail. In FIG. 1, reference numeral 16 denotes a differential amplifier as a photodetector correcting means. The differential amplifier 16 is provided between each output side of the output light detector 12 and the return light detector 22 and the power display 13. The differential amplifier 16 receives the outputs of the output photodetector 12 and the return photodetector 22 and corrects the output of the output photodetector 12 with the output of the return photodetector 22 described above. It has the function to do.

As shown in FIG. 1, the output stages of the output photodetector 12 and the return photodetector 22, as shown in FIG. 2
, And first and second coefficient adjusters 12B and 22B for individually correcting the amplified outputs of the detector outputs 12 and 22, respectively.

Next, the operation of the above embodiment will be described.

The laser light A0 output from the YAG laser oscillator 101 is partially reflected by the beam splitter 11, as shown in FIGS. The reflected output light a is captured by the output light detector 12 as a laser power detector and converted into an electric signal proportional to the output. The output signal 12a of the output photodetector 12
Is input to the differential amplifier 16 through the first amplifier 12A and the first coefficient adjuster 12B. Here, the output signal 12
a is actually drifted by the reflected return light B1 as described later (see FIG. 2).

On the other hand, the laser output light A transmitted through the beam splitter 11 is incident on the optical fiber 20B by the fiber incident lens 20A. The laser beam output from the optical fiber 20B is processed by the condensing lens 20C.
The laser beam is focused on the workpiece 2 and the workpiece 102 is laser-processed.

Here, at the time of laser processing, the workpiece 102
There is more reflected laser light. This reflected laser light is reflected on the optical axis, re-enters the optical fiber 20B by the condenser lens 20C, and is directly reflected by the reflected light B
And reaches the beam splitter 11. This reflected return light B0 is partially reflected by the beam splitter 11. The return light b reflected by the beam splitter 11 is converted by the return light detector 22 into an electric signal proportional to the amount of reflected light. Thereafter, the return light detector 22
Is input to the differential amplifier 16 through the second amplifier 22A and the second coefficient adjuster 22B.

On the other hand, the reflected return light B1 of the component transmitted through the beam splitter 11 returns to the laser oscillator 101, and is reflected by the laser output reflecting mirror 101A coaxially with the laser output light A0 described above. A part of the reflected return light B1 reflected by the beam is reflected by the beam splitter 11. As a result, the reflected return light B1 is incident again on the output light detector 12 like the monitor light a of the laser output light A0, and the output signal is output. a will drift by that much.

The monitor signal 12a drifted by the reflected return light B1 and detected by the beam splitter 11 and multiplied by a predetermined coefficient is input to the differential amplifier 16 as shown in FIGS. However, it is detected by the return light detector 22 described above in advance and the second
By taking the difference from the reflected return light signal 22b adjusted to have the same level as the drift amount by the coefficient adjuster 22B, the drift amount is canceled. As a result, a correct monitor signal a0 is output.

That is, after the signal of the return light detector 22 monitoring the reflected return light B is multiplied by an appropriate coefficient through the coefficient adjuster 22B, the signal is applied to the drifted laser output monitor signal (output light detection signal). From the output of the vessel 12). Such calculation is performed by the differential amplifier 16 described above. This enables accurate and stable laser power monitoring that is not affected by reflected return light even during laser processing.

[0033]

As described above, according to the present invention, the monitor signal of the reflected return light, which has been separately captured in advance, is subtracted from the monitor signal of the laser output light that has been drifted by the reflected return light from the laser workpiece. Since the amounts are offset, it is possible to provide an unprecedented excellent laser power monitoring device capable of performing accurate power monitoring even if there is reflected return light from a laser workpiece.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing an example of correcting an emitted light signal by the device disclosed in FIG. 1;

FIG. 3 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 11 beam splitter 12 output photodetector 12B first coefficient adjuster 13 power indicator 16 differential amplifier 22 return light detector 22B second coefficient adjuster 101 laser oscillator 102 processed object A0 laser output light B0 reflected return light a Part of output light b Part of return light a0 Monitor signal of output light

Claims (5)

[Claims] A beam splitter disposed on an optical axis of a laser beam output from a laser oscillator toward a workpiece to reflect a part of the laser beam; and detecting a laser beam reflected by the beam splitter. An output light detector, and a laser power monitoring device comprising: a power indicator for displaying an output level of laser light output from the laser oscillator based on the laser light detected by the output light detector; A return light detector for detecting a part of reflected return light from the workpiece reflected by the splitter is provided along with the beam splitter, and an output light signal detected by the output light detector is detected by the return light detection. A laser indicating the power of the output of the laser oscillator corrected by the reflected return light signal detected by the detector. Wamonita apparatus. 2. A beam splitter which is arranged on an optical axis of a laser beam output from a laser oscillator toward a workpiece and reflects a part of the laser beam, and detects the laser beam reflected by the beam splitter. An output light detector, and a laser power monitoring device comprising: a power indicator for displaying an output level of laser light output from the laser oscillator based on the laser light detected by the output light detector; A return light detector that detects a part of the reflected return light from the workpiece reflected by the splitter is provided along with the beam splitter, and each output of the output light detector and the return light detector is input. , A photodetector correcting means for correcting the output of the output photodetector by the output of the return photodetector, the output side of the output photodetector and the output side of the return photodetector. Laser power monitor device, characterized in that equipped between the power indicator. 3. The laser power monitoring device according to claim 2, wherein said photodetector correction means comprises a differential amplifier. 4. The system according to claim 1, wherein each output stage of the output photodetector and the return photodetector is provided with a coefficient adjuster for individually correcting the output of each detector. Laser power monitoring device. 5. The laser power monitor according to claim 2, wherein a digital display system is adopted as said power display.