JPH08186318A - Q-switch control apparatus - Google Patents

Abstract

PURPOSE: To provide a Q-switch control apparatus by which the output of a Q-switch can be changed properly in a state that the frequency of a pulse signal has been made constant. CONSTITUTION: A Q-switch 7 which is ON-OFF-operated by a high-frequency electric signal so as to output a laser beam selectively is installed. A Q-switch driver 8 by which a high-frequency electric signal formed at a prescribed waveform on the basis of a control signal from a control part is supplied to the Q-switch 7 is connected to the Q-switch 7. A modulation-signal oscillator 17 by which a pulse signal at a constant frequency and at a waveform whose ON-OFF ratio of the Q-switch 7 has been changed is output is installed at the Q-switch driver 8. Then, a modulator 18 by which a high frequency is modulated to a high-frequency electric signal on the basis of the pulse signal from the modulation-signal oscillator 17 so as to be supplied to the Q-switch 7 is installed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Q switch control device, and more particularly to a Q switch control device in which the emission of laser light is controlled by a Q switch.

[0002]

2. Description of the Related Art In general, a laser is used to amplify and oscillate light by utilizing stimulated emission of radiation by atoms and molecules. Therefore, it is necessary to increase the number of atoms in a high energy state and increase the stimulated emission rather than the absorption of light by photoexciting a substance in which many atoms are gathered. Further, in order to obtain a solid-state laser light having higher light intensity and higher directivity, a resonator for confining the light and amplifying the excitation energy of the light is required.

Conventionally, for example, Nd: YAG crystal is used as a solid laser active medium, light is amplified by a resonator, and the laser light is emitted to perform desired marking and trimming on a workpiece. Many solid-state laser devices are used for cutting, welding, various types of short-time analysis, and the like.

FIG. 5 shows a conventional solid-state laser marking device which is an example of such a solid-state laser device.
Cylindrical YA, which is one of the laser crystals with excellent optical characteristics
The G rod 1 is housed at one focus position inside the cavity 2 formed of an elliptic lens barrel, and the other focus position inside the cavity 2 is excited to optically excite the atoms of the YAG rod 1. A lamp 3 is arranged in parallel with the YAG rod 1. A power supply unit 4 for supplying electric power to the excitation lamp 3 is connected to the excitation lamp 3, and the power supply unit 4 controls the timing of power supply to the excitation lamp 3 to control the excitation lamp 3. A control unit 5 for turning on and off is connected. When the excitation lamp 3 is turned on, the laser crystal of the YAG rod 1 accumulates excitation energy and emits light when the excited atoms of the YAG rod 1 return to the ground state.

On the one end side of the YAG rod 1,
A total reflection mirror 6 is arranged so as to have a predetermined distance from the end surface of the YAG rod 1, and a Q switch 7 is provided on the other end side of the YAG rod 1.
Is arranged so as to have a predetermined distance from the end face of the. Further, the Q switch 7 is connected to a Q switch driver 8 that applies a voltage to operate the Q switch 7 at a specific frequency in response to a drive signal from the control unit 5. A cooler unit 9 for cooling the cavity 2 and the Q switch 7 is connected to the unit 5.

The Q switch 7 is, as shown in FIG.
An antireflection coating 10 is provided on both sides and a synthetic quartz glass 11 is disposed inside. The lower end surface of the synthetic quartz glass 11 is bonded with a piezoelectric body 13 via an adhesive layer 12. There is. Furthermore, the piezoelectric body 13 has
For example, an impedance matching circuit 14 that matches the characteristic impedance of 50Ω is connected, and the impedance matching circuit 14 is connected to an input terminal 15 for inputting the voltage from the Q switch driver 8.

Further, the Q switch driver 8 is shown in FIG.
As shown in FIG. 1, in response to the drive signal from the control unit 5, for example, a high frequency oscillator 16 that oscillates a high frequency of 24 MHz and a modulation signal oscillator 17 that oscillates 1 to 50.
A modulator 18 that modulates the high frequency into a high frequency electric signal based on a pulse signal of kHz, and a power amplifier 19 that amplifies the modulated high frequency electric signal to about 50 to 70 W and supplies the amplified high frequency electric signal to the Q switch 7. ing. Further, as shown in FIG. 8, the modulation signal oscillator 17 is provided with a V-F converter 20 to which a predetermined control voltage is applied to form a square waveform having a frequency corresponding to the control voltage, and the V-F converter 20.
The pulse waveform output from the −F converter 20 has a constant width, for example, a waveform shaping circuit 21 including a one-shot multivibrator, and as shown in FIG. Accordingly, the V-F converter 20 forms and outputs a pulse train having a predetermined frequency, and the waveform shaping circuit 21 makes the width of the pulse waveform output from the V-F converter 20 uniform to a predetermined width. It is designed to output to 18.

The Q sent from the control unit 5 is
Based on a drive signal that controls the amount of voltage applied to the switch 7 and the timing thereof, the high frequency oscillator 16 outputs 2
1 to 50 kHz oscillated by a high frequency of 4 MHz and oscillated by the modulator 18 from the modulation signal oscillator 17
The high frequency is modulated into a high frequency electric signal having a predetermined waveform based on the waveform of the pulse signal, and the power amplifier 19 amplifies the modulated high frequency electric signal to about 50 to 70 W, and then Q is input via the input terminal 15. It is supplied to the switch 7. In this way, the high frequency electric signal supplied from the Q switch driver 8 is controlled by the impedance matching circuit 14 to 50
By supplying to the piezoelectric body 13 while matching the characteristic impedance of Ω, the piezoelectric body 13 is operated and the synthetic quartz glass 11 is driven. As a result, the Q switch 7
Is turned off and the incident laser light is diffracted.

A semi-transparent output mirror 22 is provided on an extension line connecting the YAG rod 1 and the Q switch 7.
This output mirror 22 transmits a part of the laser light passing through the Q switch 7 without being diffracted when the Q switch 7 is turned on.

Further, a scanner section 23 is disposed on the laser light output side of the output mirror 22, and the laser light from the output mirror 22 is directed downward inside the scanner section 23. At the same time, two movable mirrors (not shown) for scanning in the X-Y directions are incorporated. A lens 24 is attached to the emitting portion of the scanner unit 23, and a marking material 25 is arranged at the focal position of the lens 24.

In such a conventional solid-state laser marking device, first, the excitation lamp 3 is caused to emit light by supplying electric power from the power source section 4 to the excitation lamp 3 in response to a control signal from the control section 5. At this time, since the light of the excitation lamp 3 travels radially, there are some cases where the light does not travel directly to the YAG rod 1 and collides with the inner wall of the cavity 2, but the cavity 2 is an ellipse. Since the excitation lamp 3 and the YAG rod 1 are formed at the respective focal points in the elliptical lens barrel of the cavity 2, all the light that collides with the inner wall of the cavity 2 and is reflected is formed. YAG rod 1
The atoms in the YAG rod 1 can be efficiently excited.

Then, the excitation energy in the YAG rod 1 increases in proportion to the irradiation time by the excitation lamp 3, accumulates the excitation energy capable of oscillating the solid-state laser light with the passage of time, and further emits a steady pulse. In order to reach the saturation state, the state where the necessary excitation energy is accumulated is reached. The atoms thus excited into a high energy state emit a part of energy as light in the process of returning to the original ground state. These lights are emitted by spontaneous emission. Of these lights, spontaneous emission light emitted in the axial direction of the YAG rod 1 forms a resonance state in which phases are aligned, which causes stimulated emission. It is caused to increase the light intensity and oscillate the solid-state laser light.

On the other hand, the high frequency oscillated by the high frequency oscillator 16 based on the drive signal from the controller 5 is modulated into a high frequency electric signal by the modulator 18 based on the pulse signal oscillated from the modulation signal oscillator 17. Then, after the high frequency electric signal modulated by the power amplifier 19 is amplified, it is supplied to the Q switch 7 via the input terminal 15. The high frequency electrical signal supplied from the Q switch driver 8 is passed through the impedance matching circuit 14 to the piezoelectric body 1.
3 to operate the piezoelectric body 13. In this state, light traveling straight from the YAG rod 1 in its axial direction is diffracted by the Q switch 7 to suppress laser oscillation, and light is continuously emitted by the excitation lamp 3.
Enough energy is accumulated in the YAG rod 1 to oscillate a predetermined laser beam.

Then, when the amplitude of the high frequency electric signal formed into a predetermined waveform by the modulator 18 becomes a predetermined threshold value or less as shown in FIG. 10, the high frequency electric signal is supplied to the piezoelectric body 13. It will not be done, the Q switch 7
Turns on. At that moment, laser oscillation occurs in a short time, and the laser light emitted from the YAG rod 1 passes through the Q switch 7 and a part thereof passes through the output mirror 22.

After that, the laser beam transmitted through the output mirror 22 is incident on the scanner section 23, and the scanning direction is polarized by the two movable mirrors in the scanner section 23 and is scanned in the direction of the marking material 25. While being written, writing is performed on the marking material 25 through the lens.

By repeating the above operation, desired writing is performed on the marking material 25.

[0017]

However, in the above-mentioned conventional solid-state laser marking apparatus, when the peak output of the Q-switch pulse laser is changed, as shown in FIG. 11, the pulse signal output from the modulation signal oscillator is changed. I try to change the frequency. That is, if the frequency of the pulse signal is kept small, the energy accumulated inside the YAG rod 1 increases, so that the output of the laser beam output when the Q switch is turned on increases and the frequency of the pulse signal increases. Then, since the energy accumulated inside the YAG rod 1 is small, the output of the laser light output when the Q switch is ON is small.

Therefore, in such a conventional control method, when the laser output by the Q switch is changed,
Since the frequency of the pulse signal is changed,
There is a problem in that the frequency of the pulse signal cannot be made constant, the output interval of the laser light also changes, and proper marking with the laser light cannot be performed.

The present invention has been made in view of the above points, and an object thereof is to provide a Q switch control device capable of appropriately changing the output of the Q switch while keeping the frequency of the pulse signal constant. To do.

[0020]

In order to achieve the above object, a Q switch control device according to the present invention is provided with a Q switch which is turned on and off by a high frequency electric signal to selectively output laser light. In a Q switch control device in which a Q switch driver that supplies a high frequency electric signal formed in a predetermined waveform to the Q switch based on a control signal from a control unit is connected to the switch, Constantly, the Q switch is ON,
A modulator for providing a modulation signal oscillator that outputs a pulse signal having a waveform in which the OFF ratio is changed, and modulating a high frequency into a high frequency electric signal based on the waveform of the pulse signal from the modulation signal oscillator and supplying the high frequency electrical signal to the Q switch. Is provided.

[0021]

According to the Q switch control device of the present invention, the modulation signal oscillator causes the frequency of the O switch of the Q switch to be constant.
A pulse signal having a waveform in which the ratio of N and OFF is changed is output, and a modulator modulates a high frequency into a high frequency electrical signal according to the pulse signal and supplies the high frequency electrical signal to the Q switch. For example, when the laser output is controlled to be large, the waveform of the pulse signal is made to have a long ON time and a short OFF time. When the laser output is controlled to be small, the pulse signal The waveform is designed to have a short ON time and a long OFF time. As a result, if the high frequency is modulated by a pulse waveform having a long ON time and a short OFF time of the pulse signal, the energy accumulated inside the YAG rod during the ON time becomes large.
The peak output of the laser light output when the switch is turned on becomes large, while the ON time of the pulse signal is short and the OF
When it is modulated with a pulse waveform with a long F time,
Since the energy stored inside the YAG rod is small, the peak output of the laser light output when the Q switch is ON is small.

[0022]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows one embodiment of the Q switch control device according to the present invention. The Q switch driver 8 is, for example, 24 in response to a drive signal from a control unit (not shown).
High-frequency oscillator 16 that oscillates high-frequency waves with a frequency of MHz
And 1 to 50 kHz oscillated from the modulation signal oscillator 17
The modulator 18 for modulating the high frequency into a high frequency electric signal based on the pulse signal and the power amplifier 19 for amplifying the modulated high frequency electric signal to about 50 to 70 W and supplying it to the Q switch 7. There is.

Further, the modulation signal oscillator 17 is provided with a sawtooth oscillator 26 to which a predetermined control voltage is applied and which oscillates a sawtooth corresponding to the control voltage, and a sawtooth pulse output from the sawtooth oscillator 26. A pulse width modulation circuit 2 that modulates a waveform into a pulse width according to a control signal
7 are provided.

FIG. 2 shows a concrete circuit of the modulation signal oscillator 17 and the modulator 18. In the sawtooth oscillator 26, a control voltage is applied to one side and an output signal is input to the other side. Comparator 28, and the output signal of the comparator 28 is the intermediate resistor 29 and the diode 30.
Comparator 31 input to the-side through a parallel circuit composed of
The input side of the comparator 31 is connected to its output side via the capacitor 32, and the output signal of the comparator 31 is input to the other side of the comparator 28. Has been done. Further, the pulse width modulation circuit 27 compares the output pulse from the sawtooth oscillator 26 with a predetermined control signal, modulates it to a pulse width according to the control signal, and outputs it as a rectangular pulse signal. It is composed of a container 33.

Further, the modulator 18 inputs the high frequency wave from the high frequency oscillator 16 and inputs the pulse signal from the modulation signal oscillator 17 to modulate the high frequency wave into a high frequency electric signal corresponding to the pulse signal. It is composed of a double balanced mixer 34 using diodes. The double balanced mixer 34 may be composed of, for example, a double balanced differential amplifier circuit.

Next, the operation of this embodiment will be described.

In this embodiment, as shown in FIG. 3A, the comparators 28 and 31 of the sawtooth oscillator 26 generate a sawtooth pulse signal having a predetermined pulse width in accordance with the control voltage. It is formed and output.

Next, the comparator 33 compares the pulse signal of the sawtooth waveform input from the sawtooth oscillator 26 to the pulse width modulation circuit 27 with the control signal as shown in FIG. 3B. As shown in FIG. 3C, the pulse signal is modulated into a rectangular pulse signal having a different pulse width according to the control signal and is output to the modulator 18.
In this embodiment, the pulse signal has a constant frequency and only the pulse width is changed to change the ON / OFF ratio of the waveform of the pulse signal. That is, in the case of controlling the laser output largely by controlling the control signal,
While increasing the ON time of the pulse signal waveform,
The OFF time is designed to be short, and when controlling the laser output to be small, the waveform of the pulse signal is designed to have a short ON time and a long OFF time.

When a high frequency oscillated by the high frequency oscillator 16 as shown in FIG. 3 (d) is inputted to the modulator 18, as shown in FIG. 3 (e), the double balanced The mixer 34 modulates a high-frequency electric signal having a predetermined waveform having a different pulse width in accordance with the pulse signal having a predetermined pulse width output from the modulation signal oscillator 17. After that, the high frequency electric signal is amplified by the power amplifier 19 and supplied to the Q switch 7, and when the amplitude of the high frequency electric signal becomes equal to or less than a predetermined threshold value, the Q switch 7 is turned on. Controlled as
It is designed to oscillate laser light.

In this case, as shown in FIG. 4, if the high frequency is modulated by a pulse waveform having a long ON time of the pulse signal and a short OFF time, YA is turned on during the ON time.
Since the energy accumulated inside the G rod increases, the peak output of the laser light output when the Q switch 7 is turned ON increases, while the ON time of the pulse signal is short and the OFF time is long. By doing so, the energy accumulated inside the YAG rod is small, so that the peak output of the laser light output when the Q switch 7 is turned ON becomes small.

Therefore, in the present embodiment, the modulator 18 responds to the pulse signal output from the modulation signal oscillator 17 and having a constant frequency and varying the ON / OFF ratio of the Q switch 7. Since the laser output is controlled by modulating a high frequency into a high frequency electric signal according to the pulse signal and supplying the high frequency electric signal to the Q switch 7, the frequency of the pulse signal can be kept constant. As a result, the output interval of the laser light can be controlled to be constant, and proper marking with the laser light can be performed.

In the above embodiment, the case where the Q switch control device is applied to the laser marking device has been described, but the present invention is not limited to the above embodiment, and trimming, cutting, welding and the like. It is possible to make various changes as necessary, such as applying it to the processing laser device.

[0034]

As described above, the Q switch control device according to the present invention outputs a pulse signal having a constant frequency and a waveform in which the ON / OFF ratio of the Q switch is changed, output from the modulation signal oscillator. Accordingly, the modulator controls the laser output by modulating a high frequency into a high frequency electrical signal according to the pulse signal and supplying the high frequency electrical signal to the Q switch, so that the frequency of the pulse signal is kept constant. As a result, the output interval of the laser light can be controlled to be constant, and proper marking, trimming, cutting or welding with the laser light can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a Q switch control device according to the present invention.

FIG. 2 is a specific circuit diagram of FIG.

FIG. 3 is an explanatory view showing a pulse waveform formation state by the modulation signal oscillator and modulator of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a pulse signal, a high frequency electric signal and a Q switch pulse laser output when the output control of the Q switch is performed by the control device of the present invention.

FIG. 5 is a schematic configuration diagram showing a conventional general solid-state laser marking device.

FIG. 6 is a schematic configuration diagram showing a conventional Q switch.

FIG. 7 is a block diagram showing a conventional Q switch driver.

FIG. 8 is a block diagram showing a conventional modulation signal oscillator.

FIG. 9 is an explanatory diagram showing a pulse waveform formation state by a conventional modulation signal oscillator.

FIG. 10 is an explanatory diagram showing a relationship between a conventional high frequency electric signal and laser light passing through a Q switch.

FIG. 11 is an explanatory diagram showing a relationship between a pulse signal, a high frequency electric signal, and a Q switch output when the output control of the conventional Q switch is performed.

[Explanation of symbols]

 7 Q Switch 8 Q Switch Driver 16 High Frequency Oscillator 17 Modulation Signal Oscillator 18 Modulator 19 Power Amplifier 26 Sawtooth Oscillator 27 Pulse Width Modulation Circuit

Claims (1)

[Claims] 1. A high-frequency electrical device having a Q-switch which is turned on and off by a high-frequency electrical signal to selectively output laser light, and which has a predetermined waveform based on a control signal from a control unit. In a Q switch control device comprising a Q switch driver for supplying a signal to the Q switch, a pulse signal having a constant frequency and a waveform in which the ON / OFF ratio of the Q switch is changed is supplied to the Q switch driver. A Q switch control device comprising a modulation signal oscillator for outputting, and a modulator for modulating a high frequency into a high frequency electric signal based on a waveform of a pulse signal from the modulation signal oscillator and supplying the high frequency electric signal to the Q switch. .