JPS6249757B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser output control device that intermittently emits a laser beam from a laser oscillator and can be used for machining or surgical operations.

FIG. 1 shows the configuration of a conventional laser output control device with a beam switch. A beam 1A emitted from a laser 1 is switched to a beam 1B or 1C by a beam switcher 2. The beam switching device 2 is a shutter that rotates mechanically, and one surface thereof is a reflecting surface. 2 when beam switch 2 is up
At this time, the beam 1A continues straight and becomes the beam 1B and is emitted to the outside. When the beam switching device 2 is tilted down, the beam is 2A, and the beam 1A is reflected and becomes the beam 1C, which is incident on the power sensor 3. The output of the power sensor 3 is switched on and off by a switch 4. The switch 4 is linked to the beam switch 2, and is open when the beam switch is 2B and closed when the beam switch is 2A. The memory element 5 is an element that stores the output voltage of the power sensor 3, and this voltage is applied to the feedback system 6 to control the output of the laser 1. When beam switch 2 is up (2B
) is the holding mode, and when it is falling (2A) it is the return mode. In the feedback mode, a loop of laser 1→beam switch 2→power sensor 3→feedback system 6→laser 1 is formed, and this loop is configured as a negative feedback system to stabilize the output. Since the memory element 5 is connected to the power sensor 3 in the feedback mode, the voltage value is stored therein. When the beam switch 2 is raised to emit the beam to the outside, the switch 4 is opened and feedback is removed, but the voltage stored in the memory element 5 allows the previous beam output to be maintained. This is the hold mode. In such conventional systems, an initial transient phenomenon in the feedback system occurs when the mode is switched, particularly when switching from the holding mode to the feedback mode. Therefore, the laser output during the transient time becomes unstable. At this time, since the beam is not externally emitted, instability of the externally emitted beam does not occur. However, if the beam switching operation is performed at high speed, there is a possibility that a part of this transient phenomenon will be stored in the memory element 5, and the level of the external beam will fluctuate significantly. This is shown in FIG. Since it is customary to use a thermally operated type as the power sensor 3, an output that is thermally delayed with respect to the beam incidence appears. The delay time is normally from several seconds to ten seconds. FIG. 2 shows the waveform of the power sensor output and the storage element voltage due to mode switching. If the beam switch 2 is switched sufficiently later than the heat lag of the power sensor 3, no problem will occur. However, it is entirely possible that the beam switch 2 is switched much earlier than the thermal lag time of the power sensor 3. At that time, the curve 20 in Fig. 2 (this is the power sensor 3
(the heat lag curve) is switched at 21A before it can fully rise as shown by the dotted line 21B. In that case, the voltage of the memory element 5 cannot store the normal value of 21B, but stores the value of 21A, which is not preferable.

The purpose of the present invention is to prevent the influence of transient conditions due to mode switching in a laser output control system having such a laser feedback mode switch, and by using the present invention, it is possible to prevent the effects of transient conditions due to mode switching. A storage mode that avoids transient phenomena can be generated.

FIG. 3 shows an embodiment of the present invention. The same parts as in FIG. 1 are given the same numbers, and their explanations will be omitted. 4 is a mode changeover switch. In addition, a switch 31 is provided, and a delay element 30 causes the switch to operate with a certain time delay. The switch 4 is operated in conjunction with the beam changer 2, and the delay element 3 is
0, the switch 31 is operated after a certain period of time. This lag is a unidirectional lag; it lags for a time τ only when switching from the storage mode to the return mode, and there is no lag when returning. This operation is shown in FIG. When switch 4 is in the down position (indicated by a solid line), it is in the feedback mode. At this time, the beam switching device 2 is 2A. The switch 31 falls down τ seconds after the beam switching device 2 falls to 2A (indicated by a solid line). If the time that the beam switch 2 is at 2A is shorter than τ, the switch 31 does not fall down and remains above. As soon as the beam switch 2 becomes 2B, both switches 4 and 31 are switched upward. When switch 4 is in the upper position (indicated by a broken line)
is in hold mode. The voltage of memory element 5 is applied to feedback system 6 . At this time, the switch 31 is always tilted upward and disconnected from the power sensor 3. Immediately after the beam switch 2 is switched to 2A, the switch 4 is pushed down to enter the feedback mode, and the output from the power sensor 3 is connected as an input to the feedback system 6. However, since the switch 31 does not fall down immediately, the voltage of the power sensor 3 is not immediately stored in the memory element 5. After the transient time of the power sensor 3 has passed and the voltage has stabilized (after τ seconds), the switch 31 falls down, and the memory element 5 stores the voltage of the power sensor 3 at this time. Next, when the beam switch 2 is switched to 2B, the switch 4 is switched and the laser is controlled by the voltage of the memory element 5.
In this way, the memory in the memory element 5 can escape the transient time of the power sensor 3 and the feedback system 6 due to the existence of the delay time τ, so that a steady and stable memory can be maintained as shown in FIG. When using the aforementioned power sensor with a thermal delay of several seconds to ten seconds, the appropriate delay time τ is about ten seconds.

As the delay element 30, for example, one having a configuration as shown in FIG. 5 is used. In the figure, R,
R ₁ and R ₂ are resistors, and C is a capacitor, which are used together with the comparator 51. An operating state diagram at this time is shown in FIG. When signal a' at input terminal a falls, the potential at point b falls as shown by line b'. When this potential exceeds the potential d' at point d, the comparator 51 is inverted, and the signal e' at the output terminal e drops with a delay of time τ in the figure.

As described above, the present invention provides a shutter means in the laser output section, introduces the laser beam reflected by the shutter means into the output sensor, and feeds back the laser oscillator using the output signal of the output sensor to stabilize the output. and when the laser beam is being emitted, the laser oscillator is controlled by the voltage stored in the storage means, and the feedback mode and holding mode are switched in conjunction with the operation of the shutter means, and the feedback mode In the conventional configuration, the high-speed switching of the beam switching device caused an undesirable difference in the laser output in the holding mode, but the configuration of the present invention By using this, this drawback can be completely avoided, and a storage mode that avoids transient phenomena can be created with a simple construction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional laser output control system with a beam switching device, FIG. 2 is an explanatory diagram of its operation, FIG. 3 is a block diagram showing the configuration of a laser output control device according to the present invention, 5 is a circuit diagram showing an example of a delay element used in the present invention, and FIG. 6 is a diagram explaining its operation. 1... Laser, 1A, 1B, 1C... Beam,
2...beam switcher, 2A...beam switcher for return mode, 2B...beam switcher for hold mode, 3
...Power sensor, 4...Switch, 5...Memory element, 6...Feedback system, 20...Heat lag curve, 2
1A, 21B...Power sensor output voltage, 30...
...Delay element, 31...Switch, 51...Comparator.

Claims (1)

[Claims] 1. A shutter means for intermittently outputting a laser beam from a laser tube, the laser beam reflected by the shutter means is introduced into an output sensor, and the laser tube is adjusted such that the output value of the output sensor becomes a set value. a switching means and a storage means are provided at least in the middle of the feedback means, and when the shutter means is open, the storage means and the laser tube are connected to each other, and the switching means is connected to the laser tube based on the information stored in the storage means. When the shutter means is closed, the output sensor is connected to the laser tube, and the laser tube is controlled by the output value of the output sensor, and after a certain period of time, the output sensor is also connected to the storage means. A laser output control device characterized in that the switching means and the shutter means are linked so that the output value is stored in the storage means.