JP2003017787A - Drive circuit for solid state laser device and Q switch driver - Google Patents

Abstract

(57) [Problem] To suppress damage to an optical element even if a pulse signal for performing a Q switch operation has a missing pulse. SOLUTION: In the solid-state laser device 10 provided with an AO-Q switch crystal 18 provided in a laser resonator and an AO-Q switch driver 24 for applying a voltage to the AO-Q switch crystal 18, A first trigger signal generating circuit 20 for outputting a trigger signal for operating the -Q switch driver 24 at a predetermined cycle;
And a second trigger signal generating circuit 22 for separately generating a trigger signal when an abnormality occurs in the trigger signal output from the trigger signal generating circuit 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a solid-state laser device and a Q switch driver.

[0002]

2. Description of the Related Art A YAG laser oscillator using an electro-optical Q switch (AO-Q switch) crystal inputs a trigger signal output from a trigger signal generating circuit to a Q switch driver, and based on the input trigger signal. By supplying high frequency power generated by
It is configured to generate a switch pulse laser.
If the trigger signal is omitted for some reason, the laser light generated by the next trigger may become a giant pulse and damage optical components. As a technique related to the solution of such a problem, Japanese Utility Model Laid-Open No. 5-62061 discloses “a circuit that monitors a time interval at which an input signal (pulse) is input, and disables the input signal (pulse) for a certain period. And a timer circuit for performing direct detection of the oscillated laser light by a high-speed detection circuit and comparing the input signal with the input signal in real time. In addition, JP-A-10-19011
In the publication No. 7, in order to prevent the first pulse problem from occurring, as described in the column, the light intensity of the output laser light is monitored so that the light intensity reaches a set value.
A technique for setting an attenuation factor for driving an O element is described.

[0003]

However, what can be said in common with these known techniques is that the laser operation is controlled based on the information obtained by detecting the laser beam as the output. Therefore, when an abnormality is detected in the output laser light, the optical system inside the resonator, the laser optical system outside the resonator, and the object to be irradiated with the laser light are affected. . For this reason, when the laser light is made into a giant pulse, there is a drawback that the optical components are already damaged when the abnormality is detected. Further, there is a possibility that the workpiece may be damaged during laser processing.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and a voltage is applied to the AO-Q switch crystal and the AO-Q switch crystal arranged in the laser resonator. A solid-state laser device including an AO-Q switch driver for operating the AO-Q switch driver, the first trigger signal generating circuit outputting a trigger signal at a predetermined cycle, and the first trigger signal. The solid-state laser device is configured to stop the laser operation of the solid-state laser device when an abnormality occurs in the trigger signal output from the generation circuit. Further, in a solid-state laser device including an AO-Q switch crystal arranged in a laser resonator and an AO-Q switch driver for applying a voltage to the AO-Q switch crystal, the AO-Q switch driver is operated. A first trigger signal generating circuit for outputting a trigger signal for performing a predetermined cycle and a trigger signal separately generated when an abnormality occurs in the trigger signal output from the first trigger signal generating circuit. And a trigger signal generating circuit (2). In addition, the AO-Q arranged in the laser resonator
In a solid-state laser device including a switch crystal and an AO-Q switch driver for applying a voltage to the AO-Q switch crystal, a first pulse signal for operating the AO-Q switch driver is output at a predetermined cycle. A pulse signal generating circuit; and a second pulse signal generating circuit that separately generates a pulse signal when a pulse dropout occurs in the pulse signal output from the first pulse signal generating circuit. Solid-state laser device.

Further, the AO- arranged in the laser resonator
Q switch crystal, AO-Q switch driver for applying voltage to the AO-Q switch crystal, and AO-Q switch driver
In a solid-state laser device including a drive circuit for driving a -Q switch driver, the drive circuit includes a first trigger signal generation circuit capable of outputting a pulse signal at a predetermined cycle, and the first trigger signal generation circuit. A monitor circuit connected to the output terminal of the monitor circuit for outputting a predetermined signal when the pulse signal is not detected within a predetermined time; and a second pulse circuit for outputting a single pulse signal based on the signal output from the monitor circuit. And the output signal from the second trigger signal generating circuit is combined to produce the A signal.
The solid-state laser device is characterized in that it is configured to output to an O-Q switch driver. Also, the solid-state laser device is configured so that an output signal from the first trigger signal generating circuit is delayed by time and combined with an output signal from the second trigger signal generating circuit. Is. In addition, an AO for applying a voltage to the AO-Q switch crystal arranged in the laser resonator.
In an AO-Q switch driver drive circuit for driving a -Q switch driver, the drive circuit includes a first trigger signal generation circuit capable of outputting a pulse signal at a predetermined cycle, and the first trigger signal generation circuit. A monitor circuit connected to the output terminal of the monitor circuit for outputting a predetermined signal when the pulse signal is not detected within a predetermined time; and a second pulse circuit for outputting a single pulse signal based on the signal output from the monitor circuit. And the output signal from the first trigger signal generation circuit and the output signal from the second trigger signal generation circuit are combined and output to the AO-Q switch driver. It is a drive circuit of an AO-Q switch driver characterized by being configured.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a Q-switch YAG laser 10. This Q-switch YAG laser 1
Reference numeral 0 denotes a YAG rod 12 which is an excitation medium, an excitation module 14 for exciting the YAG rod 12, a pair of resonator mirrors 14 for resonating the light generated by the excitation, and Q.
A polarizer 16 and a Q switching element 18 arranged in the resonator for switching operation, a Q switch driver 24 for applying a driving voltage to the Q switching element 18, and a trigger for controlling the Q switch driver 24. First trigger signal generator 20 for generating a signal
A monitoring circuit 26 for monitoring the presence or absence of missing pulses in the trigger signal, and a second trigger signal generator 22 for separately generating a trigger pulse when missing pulses occur. Hereinafter, each component will be described. Excitation medium YAG
The rod 12 is made of YAG (yttrium-aluminum-
Garnet) A cylindrical shape made of crystals. In order to excite this YAG rod 12, the LD (Las
The er diode stack irradiates the side surface of the rod with laser light having a main wavelength of approximately 807 nm. This LD stack is a stack of LD arrays each having a plurality of light emitting portions formed one-dimensionally, and is arranged so that the side surface of the YAG rod 12 is irradiated with p-polarized light. For example, three LD stacks are equally arranged around the rod every 120 degrees so that the excitation distribution in the YAG rod 12 is not biased. In addition, in order to suppress an excessive temperature rise, the YAG rod 12 is arranged in a flow tube in which a cooling liquid circulates. Further, the LD stack has a structure in which cooling water is circulated inside a heat dissipation plate integrated with the LD stack.

In order to resonate the light generated by the YAG rod 12, a pair of resonator mirrors 14 are arranged in the axial direction of the YAG rod 12, and laser light is output from the output mirror 14a. Become. In order to perform Q-switching operation, Q is connected between the resonator mirror 14 and the YAG rod 12.
A switching element 18 is arranged, and a polarizer 16 is arranged between the Q switching element 18 and the YAG rod 12. The Q switching element 18 is provided with a Q switch crystal, that is, an electro-optic crystal having a function of rotating the plane of polarization based on the Pockels effect when an electric field is applied. Here, when a voltage is applied from the driver, λ / 4 is provided.
It is configured to have a function as a plate. Further, the polarizer 16 is a vertical deflector. Therefore, when voltage is applied to the Q switching element 18, Q
The polarization plane of the laser light that has reciprocated through the switching element 18 rotates by 90 degrees. Therefore, while the voltage is being applied to the Q switching element 18, the vertical deflector functions as a closed shutter, and the energy stored in the resonator increases. Then, if the application of the voltage is released, a Q switch pulse is output.

In order to perform this Q switching operation,
The Q switch driver 24, for example, has a frequency of 27 MHz and an amplitude of ± 100 V, and applies a high frequency voltage that repeats On-Off at a cycle of 5 kHz to the Q switching element 18. Further, the first trigger signal generator 20 outputs a digital trigger pulse signal for operating the Q switch driver 24. In this embodiment, the pulse width is 50 μm.
The pulse signal of s is output at 5 kHz (cycle 250 μs). The trigger pulse signal from the first trigger signal generator 20 is input to the monitoring circuit 26 to monitor for missing pulses. The monitoring circuit 26 is configured to output an alarm signal when a pulse dropout occurs. For example, an alarm signal is output when a signal having a predetermined voltage level is not input for a predetermined time. In this embodiment, an alarm signal is output when there is no digital Hi-level signal for 250 μs, for example. The alarm signal of the monitoring circuit 26 is output to the second trigger signal generator 22 so as to separately generate a pulse signal for supplementation when a pulse dropout occurs.
The second trigger signal generator 22 generates a digital single pulse signal based on the alarm signal. The output of the single pulse signal generated by the second trigger signal generator 22 is
The pulse signal generated from the first trigger generator is combined and input to the Q switch driver 24.

The operation of laser oscillation in the above structure will be described below. FIG. 2A shows a signal generated from the first trigger signal generator 20. (Normal time) At normal time, as shown in (a), 50 μs
The pulse signal of is output at 5 kHz. Therefore, the trigger signal is directly output to the Q switch driver 24 without issuing an alarm signal in the monitoring circuit 26. The Q switch driver 24 applies a high frequency voltage to the Q switch based on the input trigger signal. While the voltage is being applied to the Q switch crystal, the polarizer 16 functions as a shutter as described above, so that the Q value of the resonator increases. After that, when the voltage application to the Q switch crystal is released, the shutter is opened. Therefore, laser light of Q switch pulse is output at 5 kHz. (At the time of abnormality) The first case when a pulse dropout occurs in FIG.
The output of the trigger signal generator 20 of FIG. In the prior art, when such a pulse dropout occurs, the time until the next pulse (400 μs in the present embodiment),
Since energy is accumulated, a laser beam having an extremely high peak power is output, which inevitably damages the optical components in the resonator or the optical system components of the output laser beam. In particular, damage tends to occur because the energy density is improved in the portion where the laser is focused.

In this embodiment, when a pulse dropout occurs as shown in (b), the monitoring circuit 26 outputs an alarm signal. The second trigger signal generating circuit immediately generates a trigger pulse and combines it with the original trigger signal. FIG. 2C shows the trigger pulse generated in the second trigger signal generating circuit, and the combined signal in FIG. 2D. The time to check for missing pulses is 2
Since 50 μs is set by the monitoring circuit 26, the trigger pulse generated in the second trigger signal generator 22 has a time delay of 50 μs as compared with the case where there is no pulse omission. Therefore, the output from the driver also has a time delay corresponding to this time delay. Output from the driver to (e), Q
The voltage applied to the switching element 18 is shown. However, the time for energy accumulation (250 μs) is shorter than that in the conventional case (400 μs), so the peak value of the laser pulse is also small, and damage to optical equipment and the like can be suppressed. The application of the present invention is not limited to the YAG laser, but can be applied to other solid-state lasers. Also, it is not limited to a single rod,
For example, it can be applied to a multi-rod type in which a plurality of rods are arranged in series. The excitation source is not limited to the LD, and a flash lamp or other excitation source may be used. Also, laser power is used for various things,
The greater the power, the greater the effect of the present invention. In the case of the present embodiment, the laser power is several tens of mW.

Further, the circuit configuration can be modified in various ways. For example, the same function can be obtained even when the Hi level and the Low level are reversed. Further, various numerical values are not limited to those in this embodiment. Further, the configuration of the Q-switch laser is not limited to this embodiment, and for example, when the voltage is not applied to the Q-switching element, energy is accumulated in the resonator and the voltage is applied to the Q-switching element. The laser may be output in the case of the above. (Modification 1) In the above embodiment, the trigger pulse generated in the second trigger signal generator 22 has a time delay of about 50 μs. Therefore, the output laser pulse also has a corresponding delay, which may be adversely affected during laser processing or the like. This modification is used to correct this adverse effect, and it is possible to output laser pulses regularly even if a pulse dropout occurs. FIG. 3 shows a circuit configuration according to this modification. The difference from the first embodiment is that a time delay circuit 30 is provided between the monitoring circuit 26 and the Q switch driver 24, and before being combined with the trigger pulse generated by the second trigger signal generator 2222, The point is that the signal generated by the first trigger signal generator 20 is delayed by a predetermined time.

In the case of this modification, a time delay of 50 μs is performed. By doing so, even if a pulse dropout occurs, the signal train input to the Q switch driver 24 becomes regular, and the laser pulses output as a result are also output at substantially equal time intervals. Become. The time for causing the delay can be appropriately set based on the frequency of the trigger signal and the circuit conditions of the monitoring circuit and the like. For example, if the setting time of the monitoring circuit 26 is 300 μs, 10
The time delay may be 0 μs. (Modification 2) FIG. 4 shows a further modification. When a pulse dropout occurs, the laser operation is stopped. According to this modification, the alarm signal from the monitoring circuit 26 is input to the Q switch driver 24, and the Q switch driver 24 stops applying the voltage to the Q switching element 18 based on the alarm signal. . Therefore, when a pulse dropout occurs, the laser operation is stopped, and damage to optical elements and the like can be prevented in advance. The alarm signal may be output to the excitation source to stop the irradiation of the excitation light.

[0013]

According to the present invention, the Q switch driver 2
Even if a pulse drop occurs in the trigger signal for operating No. 4, it is possible to prevent damage to the optical equipment of the Q-switch laser.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a Q-switch YAG laser 10 according to an embodiment of the present invention.

FIG. 2 is a diagram showing signals and the like generated from a first trigger signal generator 20.

FIG. 3 is a circuit configuration diagram according to a modification of the first embodiment of the present invention.

FIG. 4 is a circuit configuration diagram according to a further modification of the first embodiment of the present invention.

[Explanation of symbols]

10 Q-switch YAG laser 18 Q switch element 20 First trigger signal generator 22 Second trigger signal generator 26 Supervisory circuit.

Claims (6)

[Claims] 1. A Q switch crystal disposed in a laser resonator and a Q switch crystal for applying a voltage to the Q switch crystal.
In a solid-state laser device including a switch driver, the solid-state laser device includes a first trigger signal generation circuit that outputs a trigger signal for operating the Q switch driver in a predetermined cycle, and the first trigger signal generation circuit outputs the trigger signal. A solid-state laser device configured to stop the laser oscillation operation of the solid-state laser device when an abnormality occurs in the trigger signal. 2. A Q switch crystal disposed in a laser resonator and a Q switch crystal for applying a voltage to the Q switch crystal.
In a solid-state laser device including a switch driver, a first trigger signal generation circuit that outputs a trigger signal for operating the Q switch driver at a predetermined cycle, and the trigger signal output from the first trigger signal generation circuit. And a second trigger signal generation circuit for separately generating a trigger signal when an abnormality occurs in the solid-state laser device. 3. A Q switch crystal arranged in a laser resonator and a Q switch crystal for applying a voltage to the Q switch crystal.
In a solid-state laser device including a switch driver, a first pulse signal generation circuit that outputs a pulse signal for operating the Q switch driver at a predetermined cycle, and the pulse signal output from the first pulse signal generation circuit And a second pulse signal generating circuit for separately generating a pulse signal when a pulse drop occurs in the solid-state laser device. 4. A Q switch crystal arranged in a laser resonator, and a Q switch crystal for applying a voltage to the Q switch crystal.
In a solid-state laser device including a switch driver and a drive circuit for driving the Q switch driver, the drive circuit includes a first trigger signal generation circuit capable of outputting a pulse signal at a predetermined cycle, and the first trigger signal generation circuit. Connected to the output terminal of the trigger signal generation circuit,
A monitor circuit that outputs a predetermined signal when the pulse signal is not detected within a predetermined time; and a second trigger signal generation circuit that outputs a single pulse signal based on the signal output from the monitor circuit. In addition, the output signal from the first trigger signal generation circuit and the second
The solid-state laser device is configured to be combined with an output signal from the trigger signal generating circuit of and output to the Q switch driver. 5. The output signal from the first trigger signal generating circuit is delayed in time and combined with the output signal from the second trigger signal generating circuit. Item 4. The solid-state laser device according to item 4. 6. A drive circuit of a Q switch driver for driving a Q switch driver for applying a voltage to a Q switch crystal arranged in a laser resonator, wherein the drive circuit has a pulse signal at a predetermined cycle. Is connected to an output terminal of the first trigger signal generating circuit and the first trigger signal generating circuit,
A monitor circuit that outputs a predetermined signal when the pulse signal is not detected within a predetermined time; and a second trigger signal generation circuit that outputs a single pulse signal based on the signal output from the monitor circuit. And the output signal from the first trigger signal generating circuit and the first trigger signal generating circuit.
2. A drive circuit for a Q switch driver, wherein the output signal from the trigger signal generating circuit of 2 is combined and output to the Q switch driver.