JPH0520195B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a laser beam that detects the position of a laser beam emitted from a laser oscillator and corrects the deviation between the optical axis of the laser beam and the ideal optical axis. This invention relates to a beam position detection device.

[Prior Art] FIGS. 6 and 7 are explanatory diagrams of the configuration of a conventional laser beam position detection device, with FIG. 6 being a side view and FIG. 7 being a front view.

In the figure, 1 is a laser beam, 2 is an aperture member provided on the optical axis and constitutes a shift detector, 3 is four beam sensors attached to the aperture member 2,
4 is a reflecting mirror.

In the conventional laser beam position detection device having such a configuration, the laser beam 1 is emitted from a laser oscillator (not shown) and passes through the aperture member 2 . At this time, the base portion of the power of the laser beam 1 irradiates the four beam sensors 3, and the output at each position is detected. And laser beam 1
If the optical axis of is on the ideal optical axis, the detection outputs of all beam sensors will be balanced. Therefore, by detecting the imbalance in the output of each beam sensor 3, it is possible to know the deviation between the optical axis of the laser beam 1 and the ideal optical axis. Therefore, by installing a necessary number of such detection devices in the optical path of the laser beam 1 and correcting the preceding optical system with an appropriate correction means, the optical axis of the laser beam 1 can be accurately aligned along the ideal optical axis. can be transmitted.

[Problems to be Solved by the Invention] As described above, the conventional laser beam position detection device includes a displacement detector that is made of an aperture member that is provided with an aperture that allows the laser beam to pass through while cutting off part of the power. It is used. Normally, the aperture of the aperture member as described above is designed so as not to affect the shape or power of the laser beam. However, for example, in the case of a CO ₂ laser having a normal curve intensity distribution with a Gaussian mode (single mode) mode pattern, transmission power loss of about 2% occurs due to passage through the aperture member. Generally, this type of transmission path is provided with five or more reflecting mirrors. Therefore, if the above-described detector is placed after each of these reflecting mirrors, the total loss of transmitted power will reach 10% or more, resulting in energy loss. Furthermore, if the aperture of the aperture member is made larger in order to reduce power loss, the incident power will be weaker, so a sensor with higher sensitivity will be required. However, if a highly sensitive sensor is used and the laser beam is irradiated with a deviation, the power will be too strong and the sensor will be destroyed, resulting in problems such as a restriction in the detection range.

The present invention has been made in order to solve the problems of such conventional shift detectors.

[Means for solving the problem] A displacement detector consisting of a pair of ultrasonic transmitter and ultrasonic receiver is arranged symmetrically with respect to the optical axis of the processed lens, and the detection signal of this detection device is processed. This system is equipped with a transducer.

[Operation] Ultrasonic waves are projected onto the processed lens using an ultrasonic transmitter,
The transmitted ultrasound is received by an ultrasound receiver, and the time difference between the outputs of the transmitter and receiver, that is, the speed difference, is compared. Then, the position of the laser beam is detected based on the temperature change, and the position of the laser beam is shifted to the detection position by utilizing the fact that the propagation speed of the ultrasonic wave in the medium has a certain relationship with the temperature change of the medium. When this occurs, the optical axis of the laser beam is aligned with the ideal optical axis by correcting this "deviation amount."

[Embodiments of the Invention] FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, FIG. 2 is a side view of the main parts thereof, FIG. 3 is an explanatory diagram of the configuration of a transducer, and FIG. is a timing chart, and FIG. 5 is a relationship curve diagram between temperature and deviation amount.

In FIGS. 1 to 3, the laser beam is marked with the same symbol 1 as in FIGS. 6 and 7 described above. Reference numeral 7 designates a semi-convex disk-shaped machined lens with radius r, 8 an ultrasonic transmitter, and 9 an ultrasonic receiver. The pair of ultrasonic transmitter 8 and ultrasonic receiver 9 constitute a displacement detector. In the embodiment, two pairs of displacement detectors are prepared, and each pair is provided in contact with the side surface of the processing lens 7 on the X-axis and Y-axis passing through the optical axis O.
The optical axis O practically corresponds to the ideal optical axis of the laser beam 1. 10 is a transducer having the same configuration for processing signals on the X-axis side and the Y-axis side.
11 is a transmitter in the transducer 10;
2 is a timing circuit, 13 is an R-S flip-flop, 14 is a preamplifier, 15 is an arithmetic circuit, 1
6 is a filter, and 17 is a comparator.

The operation of the present invention having the above-described structure will now be described with reference to FIG. 4.

In the process in which the laser beam 1 enters the processing lens 7 and is focused, an electrical signal of a frequency composed of the oscillator 11 is oscillated within a time corresponding to the pulse width of the pulse generated by the timing circuit 12 on the X-axis side, for example. Ru. At the same time as the ultrasonic transmitter 8 generates ultrasonic waves of the above frequency, the R-S flip-flop 13 is set. Ultrasonic transmitter 8
When the generated ultrasonic waves propagate through the medium of the processing lens 7 and reach the ultrasonic receiver 9, the R-S flip-flop 13 is reset. On the other hand, the ultrasonic waves that reach the ultrasonic receiver 9 are converted into electrical signals here. The converted electrical signal is amplified by a preamplifier 14, and then a filter 16 removes noise such as high frequency components. The output signal of the filter 16 is compared with a reference voltage of a voltage divider by a comparator 17, and its waveform is shaped. A to H in FIG. 4 are time charts of each of the above operations, where the width T of the output pulse of the R-S flip-flop 13 indicates the propagation time required for the ultrasonic wave to pass through the processing lens 7, and the output waveform is on the X axis. This corresponds to the mode pattern of

Now, when the optical axis of the laser beam 1 coincides with the optical axis O of the processing lens 7, the center of the Gaussian mode output curve is at point O on the X-axis, and the medium temperature θ at this point is the highest, causing ultrasonic waves. The propagation speed of is maximum,
Therefore, the propagation time will be the shortest. Further, if a deviation amount δ occurs between the optical axis of the laser beam 1 and the optical axis O of the processing lens 7, the center of the Gaussian mode curve described above deviates from the optical axis O of the processing lens 7. The medium temperature θ on the X-axis is the deviation δ from the optical axis O.
It decreases in proportion to the amount, and the propagation time of the ultrasonic wave increases. From these time differences, a speed difference is determined by the arithmetic circuit 15 from the known radius r of the processing lens 7, etc., and can be output as the temperature θ. FIG. 5 is a relationship curve diagram showing the change in temperature θ with respect to the deviation amount δ of the laser beam 1. By correcting the processing lens 7 or the preceding optical system for the deviation amount δ in the X-axis direction obtained in this way, the two optical axes can be brought into alignment. On the Y-axis side, the operation is exactly the same as above,
The amount of deviation δ on the Y axis from the optical axis of the laser beam 1 can be detected and corrected.

In addition, although the above-mentioned embodiment illustrated the case where the shift detection device was attached to the processing lens, it is also possible to use other optical systems in the transmission path, such as a bend mirror. Moreover, although two pairs of ultrasonic transmitters and ultrasonic receivers have been illustrated and explained, the present invention can be practiced with one pair or three or more pairs.

[Effects of the Invention] As explained above, according to the present invention, a "deviation detector" consisting of a pair of ultrasonic transmitter and ultrasonic receiver is disposed opposite to each other in an optical system provided in a transmission path. , the ultrasonic wave was projected from the "slip detector" into the optical system. The position of the laser beam is detected by utilizing the fact that the propagation velocity of ultrasonic waves in the medium of the optical system has a constant relationship with the temperature change at each point in the medium. Therefore, according to the present invention, no power loss occurs due to laser beam position detection. In addition, since light is detected using sound waves, non-contact detection is possible without mutual interference, and even if the beam deviates from the optical axis, it will not destroy the sensor or limit the detection range as mentioned above. do not have.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, FIG. 2 is a side view of its main parts, FIG. 3 is an explanatory diagram of the configuration including a transducer, A to H in FIG. 4 are timing charts, and FIG. FIG. 5 is a diagram showing a relationship between temperature and deviation amount, and FIGS. 6 and 7 are explanatory diagrams of the configuration of a conventional laser beam position detection device. FIG. 6 is a side view, and FIG. 7 is a front view. In the figure, 1 is a laser beam, 7 is a processing lens, 8 is an ultrasonic transmitter, 9 is an ultrasonic receiver, 10
is a transducer, 11 is an oscillator, 12 is a timing circuit, 13 is an R-S flip-flop,
14 is a preamplifier, 15 is an arithmetic circuit, 16 is a filter, 17 is a comparator, T is propagation time, θ
is the medium temperature of the optical system, and δ is the amount of deviation of the laser beam. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A laser processing device that performs laser processing by focusing a laser beam emitted from a laser oscillator onto a workpiece on a processing table via an optical system provided in a transmission path, comprising: A displacement detector consisting of a pair of ultrasonic transmitter and ultrasonic receiver is placed at a symmetrical position with respect to the optical axis, and the ultrasonic waves generated by the displacement detector are propagated in the medium of the optical system. A laser beam position detection device characterized in that the position of a laser beam is detected by utilizing the fact that the speed changes in accordance with the temperature of the medium. 2. The laser beam position detection device according to claim 1, wherein a condensing lens is used as the optical system. 3. The laser beam position detection device according to claim 1, wherein a bent mirror is used as the optical system.