JP3188947B2 - Q switch control device - Google Patents

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 performs amplification and oscillation of light using stimulated emission of radiation by atoms and molecules. Therefore, it is necessary to increase the number of atoms in a high energy state by photoexciting a substance in which a large number of atoms are collected, so that stimulated emission is more than absorption of light. In order to obtain 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.

[0003] Conventionally, for example, using a Nd: YAG crystal as a solid laser active medium, light is amplified by a resonator, and this laser light is emitted to produce a desired marking, trimming, or the like on a workpiece. Solid-state laser devices used for cutting, welding, various kinds of short-time analysis, and the like are widely used.

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

[0005] Also, one end of the YAG rod 1
A total reflection mirror 6 is disposed so as to have a predetermined distance from an end surface of the YAG rod 1, and a Q switch 7 is provided at the other end of the YAG rod 1.
Are arranged so as to have a predetermined interval with respect to the end face of the. Further, the Q switch 7 is connected to a Q switch driver 8 for applying a voltage to operate the Q switch 7 at a specific frequency in accordance with 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 anti-reflection coating 10 is applied to both side surfaces, and a synthetic quartz glass 11 is provided inside. A piezoelectric body 13 is adhered to a lower end surface of the synthetic quartz glass 11 via an adhesive layer 12. I have. Further, the piezoelectric body 13 includes:
For example, an impedance matching circuit 14 that matches a characteristic impedance of 50Ω is connected, and an input terminal 15 for inputting a voltage from the Q switch driver 8 is connected to the impedance matching circuit 14.

[0007] The Q switch driver 8 is provided as shown in FIG.
As shown in (1), in response to a drive signal from the control unit 5, for example, a high-frequency oscillator 16 oscillating a high frequency of 24 MHz and 1 to 50 oscillated from a modulation signal oscillator 17
A modulator 18 modulates the high frequency into a high frequency electric signal based on a pulse signal of kHz, and a power amplifier 19 which 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 includes a VF converter 20 to which a predetermined control voltage is applied to form a square waveform having a frequency corresponding to the control voltage,
And a waveform shaping circuit 21 composed of, for example, a one-shot multivibrator for adjusting the width of the pulse waveform output from the -F converter 20 to a constant width. As shown in FIG. Accordingly, the VF converter 20 forms a pulse train of a predetermined frequency and outputs the same, and the waveform shaping circuit 21 adjusts the width of the pulse waveform output from the VF converter 20 to a constant width, and modulates the modulator. 18 is output.

The Q sent from the control unit 5
Based on the amount of voltage applied to the switch 7 and the drive signal for controlling its timing, the high-frequency oscillator 16
A high frequency of 4 MHz is oscillated, and a modulator 18 oscillates from a modulation signal oscillator 17 to 1 to 50 kHz.
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 modulated high frequency electric signal is amplified by the power amplifier 19 to about 50 to 70 W. It is supplied to the switch 7. In this way, the high frequency electric signal supplied from the Q switch driver 8 is
The synthetic quartz glass 11 is driven by operating the piezoelectric body 13 by supplying the piezoelectric body 13 with the impedance matching the characteristic impedance of Ω. Thereby, the Q switch 7
Is turned off, and the incident laser light is diffracted.

On the extension line connecting the YAG rod 1 and the Q switch 7, a semi-transparent output mirror 22 is provided.
The output mirror 22 is configured to transmit a part of the laser beam that passes through the Q switch 7 without being diffracted when the Q switch 7 is turned on.

Further, a scanner section 23 is provided on the output side of the output mirror 22 for outputting the laser beam. Inside the scanner section 23, the laser beam from the output mirror 22 is directed downward. In addition, two movable mirrors (not shown) for scanning in the XY directions are built in. A lens 24 is attached to an emission portion of the scanner unit 23, and a mark-receiving material 25 is arranged at a focal position of the lens 24.

In such a conventional solid-state laser marking device, first, power is supplied from the power supply unit 4 to the excitation lamp 3 in accordance with a control signal from the control unit 5 so that the excitation lamp 3 emits light. At this time, since the light of the excitation lamp 3 travels radially, some of the light may not directly travel toward the YAG rod 1 but impinge on the inner wall of the cavity 2. Since the excitation lamp 3 and the YAG rod 1 are arranged at respective focal points in the elliptical lens barrel of the cavity 2, all of the light colliding with the inner wall of the cavity 2 and reflected is formed by the lens barrel. YAG rod 1
And the atoms in the YAG rod 1 can be efficiently excited.

The pumping energy in the YAG rod 1 increases in proportion to the irradiation time by the pumping lamp 3 and accumulates pumping energy capable of oscillating solid-state laser light with the passage of time, and further emits a steady pulse. Saturation state is reached through a state in which the necessary excitation energy is stored. The atoms that have been excited to have a high energy state emit a part of energy as light during the process of returning to the original ground state. These lights are emitted by spontaneous emission. If the spontaneous emission of these lights emitted in the axial direction of the YAG rod 1 forms a resonance mode having a uniform phase, the stimulated emission is thereby caused. As a result, the light intensity is increased and solid-state laser light is oscillated.

On the other hand, the high frequency oscillated by the high frequency oscillator 16 is modulated into a high frequency electric signal by the modulator 18 based on the pulse signal oscillated from the modulation signal oscillator 17 based on the drive signal from the control unit 5. After being amplified by the power amplifier 19, the high-frequency electric signal is supplied to the Q switch 7 via the input terminal 15. The high frequency electric 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, the light that travels straight from the YAG rod 1 in the axial direction is diffracted by the Q switch 7 to suppress laser oscillation, and the light irradiation by the excitation lamp 3 is continued.
Energy large enough to oscillate a predetermined laser beam is stored inside the YAG rod 1.

When the amplitude of the high-frequency electric signal formed into a predetermined waveform by the modulator 18 falls below a predetermined threshold as shown in FIG. 10, the high-frequency electric signal is supplied to the piezoelectric body 13. 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 partially passes through the output mirror 22.

Thereafter, the laser beam transmitted through the output mirror 22 is incident on the scanner section 23, where the traveling direction of the laser beam is polarized by the two movable mirrors in the direction of the material to be marked 25 and scanned. Then, writing is performed on the material to be marked 25 via the lens.

By repeatedly performing the above operation, desired writing is performed on the material to be marked 25.

[0017]

However, in the conventional solid-state laser marking device, when changing the peak output of the Q-switched pulse laser, the pulse signal output from the modulation signal oscillator is changed as shown in FIG. The frequency is changed. That is, if the frequency of the pulse signal is kept small, the energy stored 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 stored inside the YAG rod 1 is small, the output of the laser beam output when the Q switch is turned on becomes small.

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

The present invention has been made in view of the above points, and has as its object to provide a Q switch control device capable of appropriately changing the output of a Q switch while keeping the frequency of a pulse signal constant. Is what you 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 a laser beam. A Q-switch control device comprising a switch connected to a Q-switch driver for supplying a high-frequency electric signal formed into a predetermined waveform based on a control signal from a control unit to the Q-switch. Constant, Q switch ON,
Control the OFF ratio to a value that makes the Q switch output an appropriate value.
A modulated signal oscillator for outputting a pulse signal having a controlled waveform, and a modulator for modulating a high frequency into a high frequency electric signal based on the waveform of the pulse signal from the modulated signal oscillator and supplying the modulated signal to the Q switch. It is a feature.

[0021]

According to the Q switch control device of the present invention, the frequency of the Q switch is kept constant by the modulation signal oscillator.
N, OFF ratio is a value that makes the Q switch output an appropriate value.
A pulse signal having a controlled waveform is output, and a modulator modulates a high frequency into a high frequency electric signal according to the pulse signal and supplies the high frequency electric signal to the Q switch. For example, when controlling the laser output to be large, the waveform of the pulse signal is formed so as to lengthen its ON time and to shorten the OFF time. The waveform is formed so that the ON time is shortened and the OFF time is lengthened. As a result, the ON time of the pulse signal is long,
If a high frequency is modulated by a pulse waveform with a short OFF time, the energy stored inside the YAG rod during the ON time increases, so that the peak output of the laser light output when the Q switch is ON increases. On the other hand, if the pulse signal is modulated by a pulse waveform with a short ON time and a long OFF time, the energy stored inside the YAG rod is small, so that the peak output of the laser light output when the Q switch is ON. Is smaller.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an embodiment of a Q-switch control device according to the present invention. A Q-switch driver 8 operates, for example, in accordance with a drive signal from a control unit (not shown).
High frequency oscillator 16 that oscillates high frequency of MHz
And 1 to 50 kHz oscillated from the modulation signal oscillator 17
And a power amplifier 19 that amplifies the modulated high-frequency electric signal to about 50 to 70 W and supplies the modulated high-frequency electric signal to the Q switch 7 based on the pulse signal. I have.

The modulation signal oscillator 17 has a sawtooth oscillator 26 to which a predetermined control voltage is applied and oscillates a sawtooth according to the control voltage, and a sawtooth pulse output from the sawtooth oscillator 26. A pulse width modulation circuit 2 for modulating a waveform to a pulse width corresponding to a control signal
7 are provided.

FIG. 2 shows a specific 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 resistor 29
a and a resistor 30 in a series circuit in which the diode 30 is connected in series.
9b is an output of the comparator circuit 28 through a circuit in parallel -
(Inverting input) side, and the comparator 31 has an inverting input side connected to an output side of the comparator 31 via a capacitor 32.
One output signal is input to the other of the comparator 28. Further, the pulse width modulation circuit 27
Is a comparator 3 which compares an output pulse from the sawtooth oscillator 26 with a predetermined control signal, modulates the pulse width according to the control signal, and outputs the result as a rectangular pulse signal.
3 is comprised.

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

Next, the operation of the present 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 waveform pulse signal having a predetermined pulse width according to the control voltage. Formed and output.

Next, a pulse signal of the sawtooth waveform input from the sawtooth oscillator 26 to the pulse width modulation circuit 27 is compared with a control signal as shown in FIG. As shown in FIG. 3C, the signal is modulated into a rectangular pulse signal having a different pulse width according to the control signal and output to the modulator 18.
In this embodiment, the frequency of the pulse signal is fixed, and only the pulse width is changed, thereby changing the ON / OFF ratio of the waveform of the pulse signal. That is, when the laser output is controlled to be large by controlling the control signal,
While increasing the ON time of the pulse signal waveform,
When the laser output is controlled to be small, the ON time of the pulse signal is shortened and the OFF time is formed long.

When a high frequency oscillated by the high frequency oscillator 16 as shown in FIG. 3D is input to the modulator 18, as shown in FIG. 3E, the double balanced The mixer 34 modulates the high-frequency electric signal having a predetermined waveform with a different pulse width according to the pulse signal having a predetermined pulse width output from the modulation signal oscillator 17. Thereafter, 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 falls below a predetermined threshold, the Q switch 7 is turned on. Is controlled as
It oscillates laser light.

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

Therefore, in this embodiment, the modulator 18 responds to a pulse signal output from the modulation signal oscillator 17 and having a constant frequency and a waveform in which the ON / OFF ratio of the Q switch 7 is changed. 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 modulated 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 appropriate marking by the laser light can be performed.

In the above embodiment, the case where the Q-switch control device is applied to a laser marking device has been described. However, the present invention is not limited to the above-described embodiment, but includes trimming, cutting, welding and the like. Various changes can be made as necessary, for example, by applying the present invention to a processing laser device.

[0034]

As described above, the Q-switch control device according to the present invention converts the pulse signal output from the modulation signal oscillator into a pulse signal having a constant frequency and a waveform in which the ON / OFF ratio of the Q switch is changed. Accordingly, the laser output is controlled by modulating a high frequency into a high-frequency electric signal according to the pulse signal and supplying the modulated 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 beam can be controlled to be constant, and effects such as appropriate marking, trimming, cutting or welding by the laser beam can be achieved.

[Brief description of the 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 diagram showing a state of forming a pulse waveform by a modulation signal oscillator and a modulator according to the present invention.

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

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 state of forming a pulse waveform by a conventional modulation signal oscillator.

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

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

[Explanation of symbols]

 7 Q switch 8 Q switch driver 16 High frequency oscillator 17 Modulated signal oscillator 18 Modulator 19 Power amplifier 26 Sawtooth oscillator 27 Pulse width modulation circuit

Continuation of the front page (56) References JP-A-57-75482 (JP, A) JP-A-2-209780 (JP, A) JP-A-3-71684 (JP, A) JP-A-3-278489 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 3/11-3/127

Claims (1)

(57) [Claims] 1. A Q switch for selectively outputting a laser beam by turning on and off with a high frequency electric signal, wherein the Q switch has a high frequency electric wave formed into a predetermined waveform based on a control signal from a control unit. in the Q-switch control apparatus a signal formed by connecting the Q-switch driver for supplying to said Q-switch, said Q-switch driver, at a constant frequency, oN Q-switch, a proper value of Q switch output ratio of OFF
A modulation signal oscillator that outputs a pulse signal having a waveform controlled to a value to be controlled; and a modulator that modulates a high frequency into a high frequency electric signal based on the waveform of the pulse signal from the modulation signal oscillator and supplies the high frequency electric signal to the Q switch. A Q-switch control device, characterized in that: