JP2844288B2 - Laser monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser monitor for monitoring the laser power of a laser beam.

[0002]

2. Description of the Related Art Laser oscillation modes are roughly classified into continuous oscillation, pulse oscillation, and Q-switch oscillation. In the laser processing field, continuous wave laser light is used for soldering, brazing, etc.
The pulsed laser light is used for spot welding, seam welding, drilling, and the like, and the Q-switched laser light is used for marking and the like. In laser processing, the energy per unit time of laser light, that is, the laser power (laser output) greatly affects the processing quality. Therefore, it is necessary to measure or monitor the value.

[0003] Conventionally, a light detection type monitoring device has been used to measure the laser power of continuous wave laser light and Q-switched laser light. In this type of monitor, a part of the laser light is made incident on a photodetector such as a photodiode, an electric signal corresponding to the light intensity of the laser light is generated, and the electric signal is integrated to obtain an average value. The measured value of the laser power is obtained from the average value. The reason why the average value is obtained by integrating instead of the instantaneous value is that the laser output often fluctuates in the case of a continuous wave laser, and the pulse width of the Q switch pulse is extremely narrow in the case of a Q switch laser. This is because it is difficult to measure the peak value (for example, 100 ns).

[0004]

By the way, a continuous wave laser beam or a Q-switched laser beam may be output intermittently. For example, in the case of laser marking, as shown by the dotted line in FIG. 4, the laser beam is applied to the workpiece at the break of the drawing line, that is, from the end of each drawing line to the start of the next drawing line. Irradiation or power is temporarily interrupted.

In the conventional monitoring apparatus, as shown in FIG. 5, a laser beam detection signal (laser output waveform) is integrated at a constant period and for a predetermined period To, and the integrated values s1, s2, s3. Is divided by the period To (integration time width) to obtain the average value of the laser light detection signal level, and the average value is converted into the average value of the laser power in each period To. In addition, since Q switch oscillation laser light is used for laser marking,
The laser light detection signal shown in FIG. 5A also includes a number of narrow pulses corresponding to the Q switch pulse. In the conventional monitor device, when the laser light is output intermittently as in this example, even if the laser output does not fluctuate particularly, the integrated values s1 and s in each period To are obtained.
.., S3..., And the average value of the laser beam detection signal level in each period To, and hence the laser power measurement value, vary, so that highly reliable monitoring could not be performed.

For this reason, in a YAG laser or the like, a value of a current supplied to a laser excitation lamp is detected, and a value of a laser power is obtained from the current value.
However, since the lamp current and the laser power do not correspond in an exact proportional relationship, such an indirect monitoring method has provided only a measured value or an estimated value as a guide.

[0007] The present invention has been made in view of the above problems, continuous onset without being affected by the laser beam interruption
Accurate laser power of vibration or Q-switched laser light
Laser monitoring with high reliability
It is an object of the present invention to provide a laser monitor device as described above .

[0008]

In order to achieve the above object, a laser monitor according to the present invention comprises a continuous wave or a Q-switch.
A laser monitoring device for monitoring the laser power of the switch oscillation Les laser light, the laser light is continuously output
Laser output period and the output of the laser light are interrupted
Laser output period discriminator to determine the laser interruption period
Stage and, by receiving a part or the whole of the laser beam, a laser beam detecting means for generating an electrical laser beam detecting signal corresponding to the laser power of the laser beam, the laser output stage
From the laser light detecting means based on the discrimination of the interval discriminating means.
Of the laser light detection signal during the laser output period only.
When the cumulative value of the integration time reaches the predetermined set time,
Outputs the final integrated value after one cycle of measurement period
An integrating means and the integrating means for each measuring period of each cycle.
And a laser power calculating means for obtaining a laser power measured value of the laser beam based on the final integrated value obtained .

[0009]

According to the present invention, a continuous oscillation or Q switch
Laser light detection signal corresponding to laser power of oscillation laser light
The integration means for integrating the signal is controlled by the laser output period determination means.
Under the control of the laser output, the laser light is continuously output.
The integration operation is performed only during the power period, and the laser light output is interrupted.
During the laser interruption period
When the integration value is set to the specified value without performing the integration operation
In the meantime, the integration action for one cycle of the measurement period
Finish the operation and output the final integrated value. Laser power calculation
The means takes the final integral value from the integrating means, and
Laser light by dividing the final integral value by the accumulated time.
Calculate the average value of the detection signal level and calculate the average
Multiplied by a given conversion factor, during the measurement period of the cycle
The measured laser power. This laser power measurement
The constant value is either continuous oscillation or measurement during the measurement period of this cycle.
Is the period during which the Q-switch oscillation laser light is actually output
Is the net laser power measurement for the measurement period
During the laser interruption period for any time, any number of times
Is also a measurement value that is not affected by this.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a configuration of a laser monitoring device according to an embodiment of the present invention applied to a laser marking device.

In this laser marking apparatus, the laser oscillation section mainly includes a YAG rod 10, an excitation lamp 12, a reflection mirror 14, an output mirror 16, a Q switch 18, and a shutter 20. The lamp current I is supplied from the laser power supply circuit 56 to the excitation lamp 12, and the excitation lamp 1
When the lamp 2 is turned on, the YAG rod 10 oscillates laser using the energy of the light from the excitation lamp 12 as the excitation energy,
Laser light LB is emitted from both end surfaces of the rod. This laser light LB is repeatedly reflected between the reflection mirror 14 and the output mirror 16 and is resonated and amplified.
Is output. The Q switch 18 is an acousto-optic element for converting a continuous wave laser beam into a high-speed repetitive pulsed laser beam. In response to a high-frequency signal from a Q switch driving circuit 58, the Q switch 18 converts the energy accumulated in the resonator to, for example, It is output at a high repetition frequency as a Q switch pulse having a pulse width of 100 ns. Most (for example, 99.9%) of the laser beam LB output from the output mirror 16
Are arranged at a predetermined angle on the optical path, for example, 0.1
% Through a beam splitter 22 having a reflectance of
It is sent to the laser emitting part.

The laser emitting section includes an X-axis rotating mirror 24, X
Axis galvanometer scanner 26, Y axis rotating mirror 2
8, Y axis galvanometer scanner 30, fθ lens 3
It is mainly composed of two. The laser beam LB coming from the laser oscillating unit first enters the X-axis rotating mirror 24, where it is totally reflected, then enters the Y-axis rotating mirror 28, and after being totally reflected by the Y-axis rotating mirror 28, fθ The work W is focused and irradiated through the lens 32. The position of the laser beam spot on the workpiece W is determined by the angle of the X-axis rotating mirror 24 in the X direction, and is determined by the angle of the Y-axis rotating mirror 28 in the Y direction. X-axis rotating mirror 24
Oscillates when driven by an X-axis galvanometer scanner 26, and Y-axis rotating mirror 28 oscillates when driven by a Y-axis galvanometer scanner 30. The scanning drive signals Fx and Fy are supplied to the scanners 26 and 30 from the galvanometer drive circuit 62, respectively. Each time the laser beam LB from the laser oscillation unit is sent, the scanners 26 and 30 respectively oscillate the X-axis rotation mirror 24 and the Y-axis rotation mirror 28 at a predetermined angle in synchronization with the laser beam LB. The beam spot of the laser beam LB is scanned on the W marking surface, and a desired drawing pattern (character, symbol,
Graphics etc.) are marked (carved).

A part (0.1%) of the laser beam reflected in a predetermined direction by the beam splitter 22 passes through a light attenuating plate 34 and attenuates its light intensity at a predetermined attenuation rate. Laser light detector 3 consisting of a photodiode
6 is incident. The laser light detector 36 outputs an electric signal corresponding to the light intensity of the received laser light LB as a laser light detection signal DS. The laser light detection signal DS is amplified by the amplifier circuit 38 and then supplied to the integration circuit 40. The integration circuit 40 integrates the input laser light detection signal DS over a predetermined cumulative time under the control of the timing circuit 42. In the present embodiment, the timing circuit 42
Responds to the integration timing control signal Jt from the CPU 46 to provide the integration circuit 40 with an integration start signal KS,
It is configured to provide an integral hold signal KH and an integral reset signal KE. When receiving the integration start signal KS, the integration circuit 40 starts or restarts the integration operation. When the integration circuit 40 receives the integration hold signal KH, the integration circuit 40 suspends the integration operation while retaining the integrated value up to that time.
Upon receiving E, the integration operation is terminated and the integration value is reset to an initial value (for example, zero). The integrated value obtained for each accumulated time by the integrating circuit 40 is converted into a digital signal by the A / D converter 44 and then converted by the CPU 46.
Given to.

The CPU 46 is a microprocessor having a built-in ROM and a RAM (not shown) or externally connected to the memory. The CPU 46 is provided with a program and an input device 48 stored in the ROM.
In accordance with the setting data stored (set and input), various controls and calculations in the monitor device and the laser marking device of the present embodiment are executed. During the laser marking processing, the CPU 46 supplies the laser oscillation output control signal GL and the Q switch control signal GQ to the laser power supply circuit 56 and the Q switch drive circuit 58 via the interface circuit 54, respectively, and drives the galvanometer via the interface circuit 60. The scanning control signal Gxy is supplied to the circuit 62. In addition, for the laser monitoring according to the present embodiment, the CPU 46 supplies the integration timing control signal Jt to the timing circuit 42 and the A / D converter 44
A predetermined calculation / judgment is performed on the basis of the digital integrated value input from the controller, the measured laser power value and the judgment result obtained by the calculation / judgment are displayed on the display device 50, or externally output via the input / output device 52. To the device.

In this embodiment, the CPU 46
The operation of the Q switch 58 is controlled by the Q switch control signal GQ, and thus the output timing of the laser light LB is controlled, and a period during which the laser light LB is output (output period) and a period during which the laser light LB is not output (interruption) Period). Therefore, the CPU 46 accumulates the output period of the laser light LB and supplies the timing circuit 42 with an integration timing control signal Jt synchronized with the timing of the output period, the interruption period, and the accumulated time.
The determination of the output period and the interruption time can be made by an external method. For example, the determination may be made from the level state of the output signal of the amplifier circuit 38.

Next, the operation of the laser monitoring apparatus according to this embodiment will be described with reference to FIG. In the laser marking apparatus as described above, when a character pattern as shown in FIG. 4 is marked on the workpiece W, for example, the output of the laser beam LB is temporarily interrupted as shown by a dotted line at a break of a drawing line. Therefore, the output terminal of the laser light detector 36 is shown in FIG.
(A), an intermittent laser light detection signal DS is obtained. The laser light detection signal DS corresponds to the output (light intensity) waveform of the laser light LB, and a pulse corresponding to a Q switch pulse having a narrow pulse width is generated at a constant period during the period when the laser light LB is being output. Repeatedly, the pulse is completely cut off during the period when the laser beam LB is not output.

In FIG. 2, when the laser light detection signal DS (laser light LB) starts to be output at time t0, an integration start signal KS is generated from the timing circuit 42, and the integration circuit 40 performs the integration operation from the initial value Sp. Start. Thus, the integrated value in the integrating circuit 40 increases in proportion to the elapse of time from the time t0. When the output of the laser light detection signal DS (laser light LB) stops at time t1, an integration hold signal KH is generated from the timing circuit 42,
The integration circuit 40 stops the integration operation. Then, the integrated value Sa1 up to that time is held as it is. Then, at time t2
Then, when the laser light detection signal DS (laser light LB) starts to be output again, the integration start signal KS is generated from the timing circuit 42, and the integration circuit 40 restarts the integration operation from the integration value Sa1. As a result, the integral value increases in proportion to the passage of time from time t2. Then, at time t3,
Cumulative time of integration operation (Ta1) from integration start time (t0)
+ Ta2) reaches the predetermined value TW, where the timing circuit 4
2, an integration reset signal KR is generated, and the integration circuit 40
Ends the integration operation, and the final integration value SA becomes the A / D converter 4
Then, the integrated value is taken into the CPU 46 via 4 and then the integrated value is reset to the initial value SP. And the timing circuit 4
2, an integration start signal KS is generated, and the same integration operation as described above is repeated. Therefore, the integral accumulation time (Tb1 + Tb2 + Tb) at the measurement time TB in the next cycle
3) is equal to Tw and the measurement time TC of the next cycle
, The integral accumulation time (Tc1 + Tc2 + Tc3) is also equal to Tw.

As described above, in the laser monitoring apparatus of this embodiment, during the period when the laser beam LB is being output (output period), the laser beam detection signal DS is integrated and the output period is included in the accumulated time. During the period in which the laser beam LB is not output (interruption period), the integrated value is held, and the interruption period is not included in the accumulated time. When the accumulated time reaches a predetermined time TW set in advance, 1 The cycle measurement period (eg, TA) ends,
The integrated value at that time (for example, SA) is taken into the CPU 46.

The CPU 46 determines the final integrated value SA
Is divided by the accumulated time TW to obtain an average value of the level or peak value of the laser light detection signal DS, and the average value is multiplied by a predetermined conversion factor. Average LB laser power (measured value) PA
Is calculated. This laser power measurement value PA is a net laser power average value during a period in which the laser beam LB is actually output in the measurement period TA of one cycle. During the measurement period TA, the interruption time is any time and any time. This is a measurement value that is not affected at all by the number of times. Therefore, when the light intensity of the laser beam LB is substantially constant, the laser power measurement values PA, PB, PC,... In the measurement periods TA, TB, TC,. Will not occur. When the light intensity of the laser beam LB fluctuates, the measurement period TA, TB, TC,.
The measured values of the laser power PA, PB, PC, ... will vary, but this is not a measurement error, but rather the actual state of fluctuation of the laser power. it can. It is also possible to set the measurement periods TA, TB, TC,... Not intermittently but intermittently.

The CPU 46 sequentially displays the laser power measurement values PA, PB, PC,... Obtained in the measurement periods TA, TB, TC,. Further, each of the measured laser power values PA, PB, PC,... Is compared with a preset reference value or monitored value, and if it is within the range of the monitored value, "good"; NG ”, and the judgment output D for each measurement period TA, TB, TC,...
A, DB, DC,... Are sent to an external device via the input / output device 52. Also, if necessary, the laser power measured value P
It is also possible to obtain an arithmetic average or a moving average of A, PB, PC,..., And if the judgment outputs DA, DB, DC,. Alternatively, the result of a typical “bad” determination may be displayed.

Although the above-described embodiment relates to a laser marking device using a Q-switch oscillation laser beam, the monitor device of the present invention can be applied to other laser devices. For example, even in a laser soldering device using continuous wave laser light, as shown in FIG. 3, continuous wave laser light may be output intermittently. The effect of is obtained. Further, the laser monitoring device of the present invention
Can be used for laser power measurement of oscillation laser light
It is .

[0022]

As described above, according to the laser monitor of the present invention, laser light is continuously output.
Integrates the laser light detection signal only during the laser output period and integrates
Measurement of one cycle when the accumulated time reaches the set time
Terminate the fixed period, and the integral value at the end (final integral value)
Of continuous wave or Q-switched laser light based on
To obtain the measured values of the laser beam.
Obtain high-precision measurements that are not affected by interruptions
Laser monitoring is possible and reliable.
Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a laser monitoring device according to an embodiment of the present invention applied to a laser marking device.

FIG. 2 is a timing chart for explaining the operation of the laser monitor device according to the embodiment.

FIG. 3 is a diagram illustrating an example of an output waveform of a laser beam to which the present invention can be applied.

FIG. 4 is a pattern diagram showing a state in which a workpiece is intermittently irradiated (output) with a laser beam in a laser marking device.

FIG. 5 is a diagram for explaining the operation of a conventional laser monitor device.

[Explanation of symbols]

 Reference Signs List 10 YAG laser rod 16 output mirror 22 beam splitter 36 laser light detector 40 integration circuit 42 timing circuit 46 CPU

Claims (3)

(57) [Claims] 1. A continuous wave or Q in laser monitoring device for monitoring the laser power switch oscillation Les laser light, the laser output period in which the laser beam is output continuously
And a laser interruption period in which the output of the laser light is interrupted,
A laser output period determining means for determining, by receiving a part or the whole of the laser beam, a laser beam detecting means for generating an electrical laser beam detecting signal corresponding to the laser power of the laser beam, the laser output Based on the judgment of the period judgment means,
The laser light detection signal from the light detection means to the laser
Integrates only during the output period, and the cumulative value of the integration time is set to a predetermined value.
When the time is reached, one cycle of the measurement
An integrating means for outputting a final integrated value, and an integrating means for obtaining the final integrated value for each measuring period of each cycle.
A laser power calculating means for obtaining a laser power measurement value of the laser light based on the final integrated value . 2. The integration means outputs the final integration value.
The integration reset is performed immediately after the
2. The laser according to claim 1, wherein the interval is started.
Monitor device. 3. The laser power calculation means calculates the laser power.
Comparing the measured laser power value with a predetermined reference value
And gives a predetermined judgment output according to the comparison result.
2. The method according to claim 1, further comprising:
The monitor device.