JPS61273290A - Laser beam machining focal position control device - Google Patents

Abstract

PURPOSE:To correct exactly a dislocation of a focal position, which is caused by an effect of a heat lens, by executing a control by using a focal position correcting signal which has been derived from a slope signal generated in proportion to an intensity signal of a laser beam, and a part of an intensity signal of a laser beam. CONSTITUTION:A laser beam 2 is irradiated to an object to be machined 6 through a lens 5, and also a part of the laser beam 2 is fetched from a beam splitter 18, and inputted to a terminal (c) of a focal position correcting signal generating circuit 20. A voltage divider 22 derives a dislocation quantity of a focal position, which is caused by a heat lens effect, based on a intensity signal of the laser beam 2. This value is outputted from a terminal (d), a machining head 4 is made to descend through a height setting device 8, by which a height of the working head 4 is controlled so as to become a proper position from the surface of the object to be machined 6. In this way, a dislocation of the focal position can be corrected exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to focal position control in a laser processing device.

[Conventional technology]

FIG. 4 is a configuration diagram showing a conventional laser processing focal position control device. In the figure, 1 is a laser oscillator, 2 is a laser beam, 3 is a pend mirror, 4 is a processing head, 5 is a lens,
6 is a workpiece, 7 is a distance detector, 8 is a height setting device, 9 is an amplifier, 10 is a servo motor drive device, and 11 is a servo motor.

FIGS. 5 and 6 are an enlarged view of a main part for explaining the operation of the laser processing focal position control device of FIG. 4, and a diagram showing the intensity of laser light, respectively.

Next, the operation of the conventional laser processing focal position control device shown in FIG. 4 will be described. A laser beam 2 output from a laser oscillator 1 is guided by a bend mirror 3 to a lens 5 of a processing head 4, and laser processing is performed with the surface of a workpiece 6 at a focal position. In addition, the distance detector 7
detects the height of the machining head 4 from the workpiece 6 and calculates the error between the detected value and the setting value of the height setting device 8 using an amplifier 9.
, thereby amplifying the servo motor drive device 10.
is operated to control the servo motor 11 so that the height of the processing head 4 is kept constant.

In this way, when laser processing the workpiece 6 using the processing head 4, when the lens 5 is irradiated with the laser beam 2 as shown in FIG. 5, the temperature of the part hit by the laser beam 2 increases. Due to the thermal lens effect of the lens 5, the focal position 12 shown by the solid line in FIG. 5 rises to focal position #13 shown by the broken line in FIG. . That is, the intensity 14 of the laser beam 2 shown in FIG. 6(a) is.

Once the laser beam 2 is irradiated onto the lens 5.

Due to the thermal lens effect l, the focal position 12 is the focal position T.
The intensity increases at t13, and the intensity of the laser beam 2 increases to 15 as shown in FIG. 6(b). In addition, when the intensity of the laser beam 2 is weak, the intensities 16 and 17 of the laser beam 2 are shown in FIGS. 6fa and 6b, respectively.

However, since the distance detector 7 detects the height of the processing head 4, this is due to the thermal lens effect described above.

Even if the focal point position changes from the surface of the workpiece 6, this cannot be detected. That rounding.

When performing laser processing such as cutting or welding on a workpiece 6 with zero nuclear force using the laser beam 2, the focal position shifts, making it impossible to perform stable laser processing. In particular, when the laser light absorption rate increases due to dirt on the lens 5, the above-mentioned focal position shift becomes noticeable.

[Problem that the invention seeks to solve]

Since the conventional laser processing focal position control device as described above has one or more configurations, there is a problem that stable laser processing cannot be performed because the focal position shifts.

This invention was made to solve such problems, and is related to laser processing. An object of the present invention is to obtain a laser processing focal position control device that can maintain a focal position at an appropriate position.

[Means for solving problems]

A laser processing focal point position control device according to the present invention.

A part of the laser beam intensity signal is added to a slope signal generated in proportion to the laser beam intensity signal.The output of the focal position correction signal generation circuit is subtracted from the processing head height setting value. This allows the height of the processing head to be controlled to an appropriate position.

[Effect]

In the laser processing focal position control device according to the present invention, the focal position correction signal generation circuit is set in accordance with the time constant due to the thermal lens effect of the lens.

By lowering the processing head by an amount equivalent to the amount that the focal position is raised by thermal lensing.

To ensure that the focal point is always kept at the same position.

〔Example〕

FIG. 1 is a schematic diagram showing a laser processing focal position control device which is an embodiment of the present invention, and each reference numeral 1 to 11 is the same as the conventional device shown in FIG. 4 above.

In the figure, 18 is a beam splitter, 19 is a laser photodetector, and 20 is a focal position correction signal generation circuit.

FIG. 2 is a diagram showing an example of a focus position correction signal generation circuit in the laser processing focus position control device of FIG. 1. In the figure, 21 is an amplifier, 22, 24 is a fractionator, 23 is a resistor, 25 is a capacitor 26, 27 is an operational amplifier, and 28 is a blade calculator.

FIG. 3 is a diagram showing a time chart of each part for explaining the operation of the g11iJ laser processing focal position control device.

Next, the operation of the laser processing focal position control device which is an embodiment of the present invention shown in FIG. 1 will be described. A laser beam 2 output from a laser oscillator 1 is guided by a pendometer mirror 3 to a lens 5 of a sword Loe head 4, and the surface of a workpiece 6 is irradiated with the laser beam 2 through this lens 5. On the other hand, a beam splitter 18 that takes out a part of the laser beam 2
The intensity signal of the laser beam 2 detected by the laser beam detector 19 is inputted to the terminal C of the focal position correction signal generation circuit 20, and the intensity signal of the laser beam 2 is input to the terminal C of the focal position correction signal generation circuit 20. value is amplified. The fractionator 22 is selected to provide an amount of correction for the intensity signal of the laser beam 2 that is equivalent to the amount of increase in the focal position due to the thermal lens effect of the lens 5. Each observational amplifier 26, 27, a resistor 23, and a capacitor 25 constitute a slope generating circuit.

Now, when the intensity signal of the laser beam 2 is output as shown in FIG. 3(e), the slope generating circuit is
) generates a slope signal output as shown in

The slope of this slope signal is determined by the resistor 23 and capacitor 25. Further, the amount of change 29 in the slope signal can be determined by the fractionator 22. The fractionator 24 is for extracting a part of the intensity signal of the laser beam 2, and is shown in FIG.
It is possible to output the output shown in g). Adder 28
adds the slope signal and a part of the intensity signal of the laser beam 2, and the output becomes the output of the terminal d of the focal position correction signal generation circuit 20. The adder 28 performs the functions shown in FIGS.
) The result of adding each output as shown in Figure 3 (h)
A waveform 30 as shown by a solid line is obtained. Figure 6(b) above
The amount of movement of the focal point position by each intensity 15 or 17 of the laser beam 2 as shown in FIG. 3(h) becomes a waveform 31 as shown by the broken line in FIG. can. That is, by subtracting the output of the terminal d of the focal position correction signal generation circuit 20 from the signal output from the height setter 8, the amount by which the focal position is raised due to the thermal lens effect of the lens 5 can be calculated. The height of the processing head 4 can be controlled to be at an appropriate position above the surface of the workpiece 6.

〔Effect of the invention〕

As explained above, the present invention has a configuration in which the laser processing focal position control device t is equipped with a focal position correction signal generation circuit for correcting fluctuations in the focal position due to the thermal lens effect of the lens. Even if changes,
Even if the lens becomes increasingly dirty, the shift in the focal position can be corrected, and as a result, a stable laser oscillator can be operated at all times, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a laser processing focal position control device which is an embodiment of the present invention, and FIG. 2 shows a focus position correction signal generation circuit in the laser processing non-point position control device shown in FIG. 1. The figure @3 shows an example. Fig. 1 is a diagram showing a time chart of each part to explain the operation of the laser processing focal position control device, Fig. 4 is a block diagram showing a conventional laser processing focal position control device, and Figs. 5 and 6 are , an enlarged view of a main part for explaining the operation of the laser processing focal position control device shown in FIG. 4, and a diagram showing the intensity of laser light, respectively. In the figure, 1... laser oscillator, 2... laser light. 3... Pend mirror - 4... Processing head, 5...
lens. 6... Workpiece, 7... Distance detector, 8... Height setting device. 9.21...Amplifier, 10...Servo motor drive device. 11... Servo motor, 12.13... Focus position -
14゜15.16.17...Intensity of laser beam 2, 18
... Beam splitter, 19... Laser photodetector,
20... Focus position correction signal generation circuit, 22.24...
- Fractionator. 23...Resistor, 25...Capacitor, 26.27.
...Operational Anne 7', 28...Katana o San i-
29... Amount of change in slope signal, 30.31... Waveform. In each figure, the same reference numerals indicate the same or equivalent parts. Figure 3 29 Nislope/Kakashiku l change amount 30.31: Liquid form

Claims (1)

[Claims] A distance detector that detects the height of the processing head of a laser processing device that focuses laser light with a lens and performs drilling, cutting, etc. on the workpiece near the focal point, and a distance detector that detects the height of the processing head. In a focal position control device that includes a controlling servo motor and a servo motor drive device, and controls the height of the processing head from the workpiece to be maintained at a set value, the height is proportional to the intensity signal of the laser beam. a focus position correction signal generation circuit that adds a part of the intensity signal of the laser beam to the generated slope signal, and an output of the focus position correction signal generation circuit for the set value of the height of the processing head; A laser processing focal point position control device characterized by subtracting .