JP4003994B2 - Solid state laser equipment - Google Patents

Description

[0010]
BACKGROUND OF THE INVENTION
The present invention relates to a Q-switch type solid-state laser device that oscillates and outputs a Q-switch pulse laser beam.
[0020]
[Prior art]
A solid-state laser device such as a YAG laser device can change continuous oscillation to high-speed repetitive pulse oscillation with a high peak output value by using a Q switch. The YAG laser device generally uses an acousto-optic Q switch that utilizes Bragg diffraction by ultrasonic waves.
[0030]
As shown in FIG. 11, the acousto-optic Q switch 100 includes a synthetic quartz glass 104 that is a polarizing medium having an entrance surface and an exit surface provided with an antireflection film 102, and an adhesive layer on one surface (bottom surface) of the quartz glass 104. A piezoelectric body 108 for generating ultrasonic waves and a high-frequency matching circuit 110 coupled via 106 are formed.
[0040]
When a high frequency electrical signal ES of 24 MHz, 50 W, for example, is given from the Q switch driver 112 to the piezoelectric body 108 via the matching circuit 110, the high frequency electrical signal ES is converted into an ultrasonic wave AS by the piezoelectric effect, and the ultrasonic wave AS is converted into the ultrasonic wave AS. Propagates through the quartz glass 104. Then, a periodic refractive index distribution is generated in the quartz glass 104 due to the photoelastic effect, and when the light LBi is incident at an appropriate angle, the incident light LBi is diffracted like LBR (acoustooptic effect). .
[0050]
FIG. 12 shows the configuration of the YAG laser resonator. A YAG rod 116 and an excitation lamp 118 are arranged in parallel at a pair of elliptical focal positions in the elliptical reflecting column 114. The output mirror 120 and the total reflection mirror 122 are disposed to face both end surfaces of the YAG rod 116, and the Q switch 100 is disposed between the one end surface of the YAG rod 116 and the output mirror 120.
[0060]
As described above, when the high frequency electrical signal ES is input to the Q switch 100 and the ultrasonic wave AS propagates in the quartz glass 104, a part of the laser light LBi from the YAG rod 116 is diffracted by the Q switch 100, and the laser resonator. Loss increases, the Q value decreases, and laser oscillation stops.
[0070]
However, even when the laser oscillation stops, the excitation of the YAG rod 116 by the excitation lamp 118 is continued, so that the inversion distribution in the YAG rod 116 (the excited state is higher than the number of atoms at a low energy level in the thermal equilibrium state). The ratio of the number of atoms at the energy level is increased). When the high frequency electric signal ES is cut off and the Q value is rapidly returned when this inversion distribution becomes sufficiently large, pulse oscillation occurs in the laser resonator, and a Q-switched pulsed laser beam LBQ having a very high peak output can be obtained. .
[0080]
In an actual application, an on period corresponding to the L level of the pulse signal MP modulated by the pulse signal MP having a desired frequency (modulation frequency) as shown in FIG. 13 and an off period corresponding to the H level of the pulse signal MP. Is supplied to the Q switch 100, whereby the Q switch pulse laser beam LBQ is oscillated and output at a repetition frequency equal to the modulation frequency.
[0090]
However, in such a Q-switch type solid-state laser device, the inversion distribution at the start of Q-switching immediately after that changes depending on the length of the on period of the high-frequency electrical signal ES, and the Q-switch pulse laser beam LBQ There is a characteristic that the peak value (laser output peak value) changes.
[0100]
For this reason, Q switching is performed in a state where the inversion distribution is generally saturated immediately after the start or restart of laser oscillation, whereas in the subsequent steady state, Q switching is generally performed before the inversion distribution reaches the saturation value. Since switching is performed, as shown in FIG. 13, the peak value of the first Q-switch pulse laser beam LBQ tends to be abnormally higher than that in the steady state.
[0110]
Such an undesired variation in the peak value of the Q-switched pulsed laser beam LBQ is an undesirable phenomenon because it causes variation in printed dots in an actual application such as a laser marking device.
[0120]
Therefore, various techniques have been devised conventionally for variably controlling the peak value of the Q-switch pulse laser beam LBQ. One of the methods is that, as shown in FIG. 14, the pulse of the pulse signal MP is not instantaneously raised from the L level to the H level, but an up-slope waveform having an appropriate gradient is used to generate a high-frequency electric signal. This is a method of turning off while attenuating the amplitude of the ES.
[0130]
According to this method, Q-switching pulse oscillation occurs when the amplitude of the high-frequency electrical signal ES divides a certain threshold value. The time until the amplitude of the high-frequency electrical signal ES divides the threshold value becomes longer as the slope or gradient of the up slope in the pulse signal MP is reduced (the loss of the inversion distribution at the start of Q switching is increased accordingly). The peak value of the Q switch pulse laser beam LBQ is lowered.
[0140]
When this method is used, as shown in FIG. 14, the peak value of the Q-switch pulse laser beam LBQ can be made constant immediately after the start or restart of laser oscillation. Alternatively, the peak value of a specific Q-switch pulse laser beam LBQ can be made higher or lower by a predetermined value than the other peak values in a steady state.
[0150]
In this type of conventional solid-state laser device, in order to realize the above-described method, a circuit for generating a modulation pulse signal is configured by an integration circuit composed of an operational amplifier, and is variable to the input or feedback loop of the operational amplifier. By providing a resistor and selecting the resistance value (that is, the integration constant) of this variable resistor to an appropriate value, the modulation pulse signal MP capable of variably controlling the upslope gradient is obtained.
[0160]
[Problems to be solved by the invention]
However, in the conventional solid-state laser device as described above, the integration constant in the integration circuit for generating the modulation pulse signal is likely to fluctuate due to the zero point fluctuation of the operational amplifier, and the up-slope gradient of the modulation pulse signal is stabilized. In addition, it is difficult to control with high accuracy, and as a result, it is difficult to freely control the peak value of the Q switch pulse laser beam LBQ. Further, if a correction circuit for increasing stability and accuracy is added around the operational amplifier, there is a problem that the entire circuit becomes complicated, expensive, and large.
[0170]
The present invention has been made in view of such problems, and controls the up-slope gradient at the time of startup of the modulation pulse signal stably and with high accuracy, and controls the peak value of the Q-switch pulse laser beam as set. An object of the present invention is to provide a solid-state laser device that can be used.
[0180]
Another object of the present invention is to provide a solid-state laser device that can control the peak value of Q-switched pulsed laser light as set with a simple configuration.
[0190]
[Means for Solving the Problems]
In order to achieve the above object, according to a first aspect of the present invention, a Q switch is provided in a laser resonator and modulated by a pulse signal having a desired repetition frequency, A high frequency electrical signal having a constant frequency having an ON period corresponding to a logic value level of the pulse signal and an OFF period corresponding to a second logic value level of the pulse signal is supplied to the Q switch, and the first logic value of the pulse signal is supplied In the solid-state laser device that controls the peak value of the Q-switched pulsed laser light oscillated and output from the laser resonator by controlling the speed of transition from the level to the second logical value level, the repetition frequency And a reference pulse signal generating means for generating a rectangular reference pulse having a constant pulse width, and a first and second control terminal connected in common to each other. And a current mirror circuit having a second transistor, connected between a terminal of a first power supply voltage and the current mirror circuit, for inputting a reference pulse and for a time corresponding to a pulse width of the reference pulse. Switch means for conducting only the first power supply voltage to the current mirror circuit, a capacitor connected between a terminal of a second power supply voltage and the first transistor, and the second power supply A resistance value variable resistance circuit connected between a voltage terminal and the second transistor; resistance value selection means for selecting a resistance value of the resistance circuit to a desired value; A discharge means for forming a circuit, allowing the capacitor to be charged only for a time corresponding to a pulse width of the reference pulse, and discharging the capacitor after the end of the time; Characterized by comprising a pulse signal output means for outputting a voltage of capacitor as the pulse signal.
[0200]
According to a second aspect of the present invention, a Q switch is provided in the laser resonator, the ON period corresponding to the first logical value level of the pulse signal modulated by a pulse signal having a desired repetition frequency, and the pulse signal A high frequency electrical signal having a constant frequency having an off period corresponding to a second logic value level of the pulse signal is supplied to the Q switch, and the pulse signal is shifted from the first logic value level to the second logic value level. In the solid-state laser device that controls the peak value of the Q-switched pulsed laser light oscillated and output from the laser resonator by controlling the speed at which the laser resonator is controlled, the solid-state laser device has the repetition frequency and a constant pulse width. A reference pulse signal generating means for generating a reference pulse having a rectangular waveform and a first and second transistor having respective control terminals commonly connected to each other. A current mirror circuit, connected between a terminal of a first power supply voltage and the current mirror circuit, receiving the reference pulse and conducting only for a time corresponding to the pulse width of the reference pulse. Switch means for supplying the first power supply voltage, a capacitor connected between the terminal of the second power supply voltage and the first transistor, the terminal of the second power supply voltage, and the second power supply voltage. A constant current source of a variable current value type connected between the transistors, a current value selection means for selecting a current value of the constant current source to a desired value, and a closed circuit with the capacitor; Discharging means for allowing the capacitor to be charged only for a time corresponding to a pulse width of a reference pulse, discharging the capacitor after the end of the time, and a voltage of the capacitor as the pulse signal. Characterized by comprising a pulse signal output means for outputting Te.
[0210]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS.
[0220]
FIG. 1 shows a configuration of a main part of a Q-switch type YAG laser processing apparatus for scanning marking according to an embodiment of the present invention.
[0230]
In this YAG laser processing apparatus, the YAG rod 10, the excitation lamp 12, the output mirror 14, the total reflection mirror 16, and the Q switch 18 constitute a YAG laser resonator (oscillator) 19 similar to that shown in FIG.
[0240]
The excitation lamp 12 receives a direct current lamp current from the power supply circuit 20 and continuously emits light. The YAG rod 10 is excited by the light irradiated from the excitation lamp 12, and emits light in the axial direction from both end faces thereof. When the application of the high-frequency electrical signal ES is stopped in the Q switch 18, the light emitted from both end faces of the YAG rod 10 repeats reflection between the output mirror 14 and the total reflection mirror 16 through the Q switch 18 and resonates. After amplification, the output mirror 14 exits in the axial direction as Q-switched pulsed laser light LBQ. The Q-switch pulse laser beam LBQ emitted from the output mirror 14 is sent to the scanning unit 22 through a transmission optical system (not shown) such as a mirror or an optical fiber.
[0250]
The scanning unit 22 includes an optical scanning mechanism for scanning the beam spot of the Q switch pulse laser beam LBQ with a desired drawing pattern on the workpiece W, a scanning drive circuit, and the like.
[0260]
The Q switch 18 may be an acousto-optic Q switch having the same configuration and function as those shown in FIG. Therefore, the Q switch 18 diffracts the incident light LBi from the YAG rod 10 by the acoustooptic effect while the high frequency electrical signal ES is supplied from the Q switch driver 26 under the control of the Q switch control unit 24. (Increase the Q value) and increase the inversion distribution in the resonator, and when the supply of the high-frequency electric signal ES is cut off, the incident light LBi advances straight (returns the Q value) to the Q switch pulse laser It functions to oscillate and output the optical LBQ.
[0270]
The main control unit 28 is composed of a microcomputer, and in accordance with a required program stored in a built-in memory and various setting values set and inputted from the setting unit 30, the power supply circuit 20, the scanning unit 22, the Q switch control unit 24, etc. To control the operation.
[0280]
FIG. 2 shows a circuit configuration of the Q switch control unit 24 in the present embodiment. The Q switch control unit 24 includes a pulse generator 32, a pulse shaping circuit 34, a modulation pulse generation circuit 36, a high frequency oscillator 38, and a modulation circuit 40.
[0290]
The pulse generator 32 is composed of, for example, a VF (voltage-frequency) converter, receives the frequency control voltage VS from the main control unit 28, and outputs the pulse signal SP at a repetition frequency proportional to the voltage level of the control voltage VS. appear.
[0300]
As schematically shown in FIG. 3, in the pulse signal SP generated by the pulse generator 32, the pulse width TSP changes in inverse proportion to the repetition frequency. That is, the lower the repetition frequency, the larger the pulse width TSP, and the higher the repetition frequency, the smaller the pulse width TSP.
[0310]
The pulse shaping circuit 34 is composed of, for example, a one-shot multivibrator, receives the pulse signal SP from the pulse generator 32, and has a constant pulse width TW in response to the rising edge of the pulse signal SP as shown in FIG. The pulse signal CP is output.
[0320]
In the present embodiment, the pulse generator 32 and the pulse shaping circuit 34 constitute reference pulse signal generation means, and the pulse signal CP having a constant pulse width output from the pulse shaping circuit 34 becomes the reference pulse.
[0330]
In FIG. 3, the level of the frequency control voltage VS with respect to the pulse generator 32 is monotonically increased with time in order to explain the function of the reference pulse signal generation means in this embodiment. The frequency control voltage VS is selected at a voltage level corresponding to the set value of the repetition frequency of the pulse laser beam LBQ.
[0340]
The modulation pulse generation circuit 36 receives the pulse signal CP from the pulse shaping circuit 34, synchronizes with the pulse signal CP as schematically shown in FIG. 3, and varies the gradient (speed) of the rising portion for each pulse. A pulse signal MP for modulation that can be controlled is generated. The modulation pulse generation circuit 36 is a main feature of the present embodiment, and its configuration and operation will be described in detail later.
[0350]
The modulation circuit 40 receives the modulation pulse signal MP from the modulation pulse generation circuit 36, and also inputs, as a carrier wave, a high-frequency electrical signal ES0 that is continuously output from the high-frequency oscillator 38, for example, at 24 MHz and 50 W. The high frequency electrical signal ES0 is modulated with the pulse signal MP in the same manner as shown in FIG. 14 to generate the high frequency electrical signal ES for Q switching.
[0360]
These three signals MP, ES0, ES have the following relationship. That is, ES is on (output) period while MP is at L level and ES0 is output as ES as it is, and ES is off (interruption) period when MP is at H level. ES0 is cut off and the amplitude of ES becomes zero level. When the MP rises from the L level to the H level and the ES switches from the ON period to the OFF period in response to this, the ES rises with the magnitude of the rising speed of the MP, that is, the decay rate proportional to the upslope gradient. Amplitude is attenuated.
[0370]
The Q switch driver 26 may be a power amplifier type drive circuit having the same configuration and function as shown in FIG. 11, and amplifies the high frequency electric signal ES from the modulation circuit 40 and supplies it to the Q switch 18.
[0380]
FIG. 4 shows a circuit configuration of the modulation pulse generating circuit 36 in the first embodiment.
[0390]
In this modulation pulse generation circuit 36, a pair of PNP transistors 42 and 44 whose base terminals are connected in common constitute a current mirror circuit 46.
[0400]
The emitter terminals of both transistors 42 and 44 are commonly connected to each other, and are electrically connected to a terminal of a power supply voltage VB (first power supply voltage) of, for example, +5 V via an NPN transistor 48. The collector terminal of the first transistor 42 is connected to the terminal of the ground potential (second power supply voltage) via the capacitor 50. The collector terminal of the second transistor 44 is connected to a ground potential terminal via a resistance circuit 52 having a variable resistance value.
[0410]
The resistance circuit 52 is electrically, optically, or mechanically connected to the resistance value selection unit 53, and the resistance value selection means 53 responds to the resistance value selection signal RS from the main control unit 28 and the resistance value selection unit 53 determines the resistance value of the resistance circuit 52. RF is selected or switched to a desired value.
[0420]
A commonly connected base terminal of both transistors 42 and 44 is connected to the collector terminal of the second transistor 44 and to the emitter terminal of the transistor 48 via the capacitor 54.
[0430]
The transistor 48 is a switch that inputs the reference pulse CP from the pulse shaping circuit 34 to the base terminal via the resistor 56 and is conductive only while the reference pulse CP is at the H level. When the transistor 48 is turned on, the power supply voltage VB is supplied to the current mirror circuit 46 through this transistor.
[0440]
A discharge circuit 61 composed of a diode 58 and a resistor 60 is connected to the capacitor 50 so as to form a closed circuit. More specifically, the anode terminal of the diode 58 is connected to the terminal 50 a opposite to the ground side of the capacitor 50, the cathode terminal is connected to the emitter terminal of the transistor 48, and the ground side terminal of the capacitor 50 is connected via the resistor 60. 50b.
[0450]
The terminal 50 a of the capacitor 50 is also connected to the base terminal of the NPN transistor 64 through the resistor 62. The transistor 64 is Darlington-connected to the NPN transistor 66, and a pulse signal output circuit 74 is constituted by the transistors 64 and 66, the bias resistors 68 and 70, and the load resistor 72.
[0460]
Next, the operation of the modulation pulse generation circuit 36 configured as described above will be described with reference to FIGS.
[0470]
While the reference pulse CP supplied from the pulse shaping circuit 34 is at the L level, the transistor switch 48 is in an off (cut-off) state, and no current flows through the current mirror circuit 46. The capacitor 50 has almost no charge, and its voltage (potential of the terminal 50a) Vc is almost 0 V (L level). In the pulse signal output circuit 74, both the amplifying transistors 64 and 66 are in the OFF state, and the modulation output pulse signal MP obtained from the emitter terminal of the transistor 66 is substantially 0 V (L level).
[0480]
When the reference pulse CP changes from L level to H level, the transistor switch 48 is turned on (conductive). The change (rise) of the reference pulse CP from the L level to the H level is based on the gradient of the rise (up slope portion) from the L level to the H level of the modulation pulse signal MP to be controlled in this embodiment. If you look at it, you can almost instantaneously move at a right angle (90 °).
[0490]
When the transistor switch 48 is turned on, the power supply voltage VB is supplied to the current mirror circuit 46 via the transistor 48, both transistors 42 and 44 are turned on simultaneously, and collector currents I1 and I2 begin to flow, respectively. At this time, the capacitor 54 applies a voltage between the emitter and base of both the transistors 42 and 44 immediately after the transistor 48 is turned on, and acts to accelerate (promote) the turning on of both the transistors 42 and 44.
[0500]
When the transistor 44 is turned on, a current I2 flows through a current path passing through the transistor 44 and the resistance circuit 52 to the ground potential. As shown in FIG. 5, there is a constant inverse proportional relationship between the resistance value RF of the resistance circuit 52 and the current I2. Based on the resistance-current characteristics, the main control section 28 selects the resistance value RF of the resistance circuit 52 to a predetermined value via the resistance value selection section 53 so that the current I2 flows at a desired current value.
[0510]
In this way, when the current I2 flows in a desired current value in the current path on the transistor 44 side, the current I1 flows in the current path on the transistor 42 side with a current value equal to the current I2 due to the current mirror effect. Most of the current I1 is supplied to the capacitor 50. A portion of the current I1 that flows to the base terminal of the transistor 64 of the pulse signal output circuit 74 is relatively very small and can be ignored.
[0520]
As a result, the capacitor 50 is charged with a substantially constant current I1, and its voltage VC rises almost linearly according to the following equation (1).
VC = I1 t / C (1)
[0530]
Here, C is a capacitance (farad) of the capacitor 50, and t is an elapsed time (seconds) after the switch transistor 48 is turned on.
[0540]
When the voltage VC of the capacitor 50 reaches a predetermined level near the power supply voltage VB, the diode 58 becomes conductive in the discharge circuit 61, and the electric charge overflowing from the capacitor 50 is discharged to the ground through the diode 58 and the resistor 60. When the discharge charge amount and the charge amount by the current I1 are balanced, the voltage VC of the capacitor 50 becomes a flat level (H level).
[0550]
The pulse signal output circuit 74 inputs the voltage VC of the capacitor 50 through the resistor 62, amplifies the voltage by both transistors 64 and 66, and outputs an output voltage having a waveform similar to the voltage VC as the pulse signal MP.
[0560]
Thereafter, when the reference pulse CP changes from the H level to the L level on the input side, the transistor switch 48 is turned off, and the terminal of the power supply voltage VB and the current mirror circuit 46 are cut off. As a result, in the current mirror circuit 46, the currents I1 and I2 are stopped in both the transistors 42 and 44.
[0570]
Then, charging of the capacitor 50 is stopped, and all the electric charge accumulated in the capacitor 50 is instantaneously discharged by the discharge circuit 61 (58, 60), and the capacitor voltage VC is instantaneously changed from the previous H level to the L level (0 volts). ). In response to this, the output voltage (pulse signal MP) of the pulse signal output circuit 74 also falls rapidly from the H level to the L level.
[0580]
In this way, as shown in FIG. 6, the modulation pulse generating circuit 36 generates a modulation pulse signal MP that is synchronized with a rectangular waveform input pulse (reference pulse CP) and that can variably control the up-slope gradient θ at the time of rising. can get.
[0590]
In this modulation pulse generation circuit 36, the upslope gradient θ of the pulse signal MP is defined by the coefficient (I1 / C) of the above equation (1), and I1 is a parameter (variable). In order to variably control I1, the main controller 28 selects the appropriate resistance value RF of the resistor circuit 52 that defines I2 equal to this value via the resistance value selector 53. .
[0600]
As shown in FIGS. 5 and 6, by selecting the resistance value RF of the resistance circuit 52 to a relatively small value Ra, the up slope gradient θ is set to a relatively large value θa, and the resistance value RF is selected to a relatively large value Rb. Thus, the upslope gradient θ can be set to a relatively small value θb.
[0610]
As described above, the modulation pulse generation circuit 36 of the present embodiment is provided with the current mirror circuit 46, and the current path on the first transistor 42 side of the pair of transistors 42 and 44 constituting the current mirror circuit 46 is provided. A capacitor 50 is connected to the current path on the second transistor 44 side, and a resistance value variable resistance circuit 52 is connected to the current path on the second transistor 44 side. Also provided is a switch means comprising a transistor 48 for operating the current mirror circuit 46 only during the pulse time of the reference pulse CP.
[0620]
Then, the resistance value RF of the resistance circuit 52 is selected to an appropriate value by the main control unit 28 via the resistance value selection unit 53, so that the current path on the second transistor 44 side during the pulse time of the reference pulse CP. The current I2 flowing in the current transistor, and the current I1 flowing in the current path on the first transistor 42 side having the same magnitude due to the current mirror effect, is selected as a desired current value, and the rising gradient (speed) of the charging voltage of the capacitor 50 is The desired size is controlled.
[0630]
The voltage VC of the capacitor 50 has a pulse waveform synchronized with the reference pulse CP by the discharge circuit 61 including the diode 58 and the resistor 60. The voltage VC of the capacitor 50 is amplified by the pulse signal output circuit 74 and output as a modulation pulse signal MP.
[0640]
As described above, in this embodiment, the up-slope gradient at the rising edge of the modulation pulse signal MP is controlled by using the stable current I1 (I2) in the current mirror circuit 46 as a parameter, so that stable and highly accurate control is possible. It is possible to control the peak value of the Q-switch pulse laser beam as set.
[0650]
FIG. 7 shows a specific circuit configuration example of the resistance circuit 52 and the resistance value selection unit 53 in the present embodiment. In this example, the resistance circuit 52 includes three resistors 74, 76, and 78 connected in series, and the resistance value selection unit 53 includes analog switches 80 and 82 that are connected in parallel to the resistors 76 and 78, respectively. .
[0660]
The analog switches 80 and 82 are on / off controlled by resistance value selection signals RS1 and RS2 from the main control unit 28, respectively. Assuming that the resistance values of the resistors 74, 76, and 78 are R74, R76, and R78, when both the switches 80 and 82 are turned off, the resistance value R53 of the resistor circuit 52 is given by (R74 + R76 + R78). When the switch 80 is turned on and the switch 82 is turned off, the resistance value R53 of the resistance circuit 52 becomes (R74 + R78). When the switch 80 is turned off and the switch 82 is turned on, the total resistance value R53 becomes (R74 + R76). When both the switches 80 and 82 are turned on, the total resistance value R53 is R74.
[0670]
In this way, in this configuration example, the resistance value R53 of the resistance circuit 52 can be selected from four values (R74 + R76 + R78), (R74 + R76), (R74 + R78), and R74. Therefore, the modulation pulse signal MP The up-slope gradient at the time of rising or the peak value of the Q-switch pulse laser beam can be variably controlled to four values.
[0680]
In general, in laser marking processing, as shown in FIG. 13, the first one or several Q-switched pulsed laser beams LBQ immediately after the start or restart of laser oscillation are abnormally higher than those at normal times. Has been. That is, there is a problem that the dots near the marking start point are formed abnormally larger than the dots at the subsequent drawing points.
[0690]
In order to deal with such a problem, only the up slope slope θ of the modulation pulse signal MP corresponding to the first to several Q-switch pulse laser beams LBQ may be set to a relatively small value. The up-slope gradient θ of the modulation pulse signal MP corresponding to the Q switch pulse laser beam LBQ may be a constant value. Therefore, if there is a function capable of selecting the upslope gradient θ with four values, it can be sufficiently handled. In that sense, the example of FIG. 7 has a simple circuit configuration and excellent practicality.
[0700]
Of course, the resistor circuit 52 is configured by a more complicated resistor network such as a ladder resistor network or a weight resistor network, and the switch element of the resistance value selecting unit 53 is provided at a required branch in the resistor circuit network. It is possible to increase the resolution of the resistance value RF of the resistance circuit 52 and hence the resolution of the upslope gradient θ of the modulation pulse signal MP.
[0710]
The resistance circuit 52 is composed of a resistance element such as a CdS element whose resistance value changes depending on the light irradiation intensity, and the resistance value selection unit 53 is a light emitting element such as an LED for irradiating the CdS element with light. By configuring the LED with a variable current source for supplying a drive current that can be variably controlled, the resistance value R F of the resistance circuit 52 and thus the up-slope gradient θ of the modulation pulse signal MP can be continuously variably controlled. it can.
[0720]
FIG. 8 shows a circuit configuration of a modulation pulse generation circuit 36 according to another embodiment. In the figure, parts having the same configuration and function as those in FIG.
[0730]
In the second embodiment, in the circuit configuration of FIG. 4, the variable resistance type resistance circuit 52 is replaced with a variable current value type constant current source 84, and the constant current source 84 is replaced with the resistance value selection unit 53. A current value selection unit 86 is provided for appropriately selecting the current value IF.
[0740]
In the modulation pulse generating circuit 36 according to the second embodiment, both the transistors 42 and 44 of the current mirror circuit 46 are in the off state while the switch transistor 48 is in the off state, so that the constant current source 84 is also in the inactive state. Current IF is not applied.
[0750]
When the switch transistor 48 is turned on in response to the reference pulse CP and both the transistors 42 and 44 of the current mirror circuit 46 are also turned on, the constant current source 84 changes to an active state, and a predetermined constant current IF flows.
[0760]
As a result, in the current mirror circuit 46, the same current I2 as the constant current IF flows in the current path on the second transistor 44 side, and the constant current IF (I2) in the current path on the first transistor 42 side by the current mirror effect. Current I1 equal to. Other operations are the same as in the embodiment of FIG.
[0770]
In this embodiment, the currents I1 and I2 flowing in the current mirror circuit 46 are controlled strictly constant by the constant current source 84, and the linearity of the rising voltage of the capacitor 50 can be controlled strictly constant. In addition, it is possible to variably control the up-slope gradient θ of the modulation pulse signal MP and the peak value of the Q-switch pulse laser beam LBQ with high accuracy.
[0780]
FIG. 9 shows a specific configuration example of the constant current source 84 and the current value selector 86 in the embodiment of FIG.
[0790]
In this configuration example, each constant current source 84 is set to I / 2. ⁿ , I / 2 ^n-1 ,..., I / 4, I / 2 weight constant current sources 88 (n), 88 (n-1), ..., 88 (2), 88 (1). , 90 (n), 90 (2), 90 (1) and n changeover switches 90 (n), 90 (n-1),. It consists of a register 92 for controlling the switching position of the switch.
[0800]
The fixed terminal of each changeover switch 90 (i) is connected to the terminal opposite to the ground side of each corresponding weighted constant current source 88 (i), and the movable terminal is connected to each corresponding output terminal Y (i) of the register 92. It is connected to either the terminal 91 or 93 according to the switching control signal given. The terminal 91 is connected to the emitter terminal of the second transistor 44 of the current mirror circuit 46. An appropriate potential (for example, 0 volts) is applied to the terminal 91.
[0810]
The register 92 is composed of, for example, an n-bit serial input / parallel output shift register, stores n-bit current value selection data IS from the main control unit 28, and switches corresponding to the bits of each digit of the data IS. A control signal Y (i) is given to each changeover switch 90 (i).
[0820]
In this configuration example, I / 2 ⁿ Resolution from 0 (ampere) to (2 ⁿ -1) ・ I / 2 ⁿ The current value IF (I2) of the constant current source 84, that is, the charging current I1 of the capacitor 50 can be variably adjusted up to (ampere).
[0830]
FIG. 10 shows a functional configuration of the main control unit 28 for controlling the peak value of the Q-switched pulsed laser beam LBQ for each pulse. The main control unit 28 counts the pulse SP (CP, MP) output from the pulse generator 32, the pulse shaping circuit 34, or the modulation pulse generation circuit 36 with the counter 94, so that what number is the next pulse. And the current setting value IS corresponding to the next pulse is obtained by calculation from various setting values (for example, peak value setting values) held in the setting value storage unit 98, and the obtained current setting value IS is digitally calculated. The data is supplied to the current value selector 86 as it is or after being converted into an analog signal.
[0840]
Even in the above-described variable resistance method (FIGS. 4 and 7), the main control unit 28 can adopt the configuration shown in FIG.
[0850]
【The invention's effect】
As described above, according to the solid-state laser device of the present invention, the up-slope gradient at the time of rising of the modulation pulse signal is controlled using the current stabilized by the current mirror circuit, so that the stable and High-precision variable control is possible, and the peak value of the Q-switch pulse laser beam can be controlled as set.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a main part of a Q-switch type YAG laser processing apparatus for scanning marking according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a circuit configuration of a Q switch control unit in the embodiment.
FIG. 3 is a waveform diagram showing signal waveforms of respective units for explaining functions of a pulse generator, a pulse shaping circuit, and a modulation pulse generating circuit in the Q switch control unit of the embodiment.
FIG. 4 is a circuit diagram showing a circuit configuration of a modulation pulse generating circuit in the first embodiment.
FIG. 5 is a diagram illustrating a relationship between a resistance value and a current value in the resistance value variable resistance circuit of the example.
FIG. 6 is a diagram showing waveforms of an input pulse and an output pulse for explaining the operation of the modulation pulse generation circuit in the embodiment.
FIG. 7 is a circuit diagram showing a specific circuit configuration of a modulation pulse generating circuit in the first embodiment.
FIG. 8 is a circuit diagram showing a circuit configuration of a modulation pulse generating circuit in a second embodiment.
FIG. 9 is a circuit diagram showing a specific circuit configuration of a modulation pulse generating circuit according to a second embodiment.
FIG. 10 is a block diagram showing a functional configuration of a main control unit in an embodiment for controlling the peak value of the Q-switch pulse laser beam for each pulse.
FIG. 11 is a diagram illustrating a configuration of an acousto-optic Q switch.
FIG. 12 is a perspective view showing a configuration of a YAG laser resonator.
FIG. 13 is a waveform diagram for explaining a method of modulating a high-frequency electrical signal supplied to an acousto-optic Q switch with a pulse signal.
FIG. 14 is a waveform diagram for explaining a method of giving an up slope to a rising portion of a modulation pulse signal in order to control a peak value of a Q-switch pulse laser beam.
[Explanation of symbols]
18 Q switch
19 YAG laser resonator (oscillator)
24 Q switch controller
28 Main control unit
46 Current mirror circuit
48 transistors
50 capacitors
52 Resistance circuit
53 Resistance value selector
61 Discharge circuit
74 Pulse signal output circuit
84 Constant current source
86 Current value selector

Claims (2)

A Q switch is provided in the laser resonator, and is modulated by a pulse signal having a desired repetition frequency, and is turned on according to the first logic value level of the pulse signal and according to the second logic value level of the pulse signal. A high frequency electrical signal having a constant frequency having an off period is supplied to the Q switch, and the laser resonance is controlled by controlling a speed at which the pulse signal shifts from a first logic value level to a second logic value level. In the solid-state laser device that controls the peak value of the Q-switched pulsed laser light that is oscillated and output from the device,
A reference pulse signal generating means for generating a reference pulse having a rectangular waveform having the repetition frequency and a constant pulse width;
A current mirror circuit having first and second transistors having respective control terminals commonly connected to each other;
Connected between a terminal of a first power supply voltage and the current mirror circuit, inputs the reference pulse, and conducts only for a time corresponding to the pulse width of the reference pulse, and then supplies the current mirror circuit to the first current mirror circuit. Switch means for supplying the power supply voltage of
A capacitor connected between a terminal of a second power supply voltage and the first transistor;
A variable resistance type resistance circuit connected between a terminal of the second power supply voltage and the second transistor;
Resistance value selection means for selecting a resistance value of the resistance circuit to a desired value;
A discharging means for forming a closed circuit with the capacitor, allowing the capacitor to be charged only for a time corresponding to a pulse width of the reference pulse, and discharging the capacitor after the end of the time;
A solid-state laser device comprising pulse signal output means for outputting the voltage of the capacitor as the pulse signal. A Q switch is provided in the laser resonator, and is modulated by a pulse signal having a desired repetition frequency, and is turned on according to the first logic value level of the pulse signal and according to the second logic value level of the pulse signal. A high frequency electrical signal having a constant frequency having an off period is supplied to the Q switch, and the laser resonance is controlled by controlling a speed at which the pulse signal shifts from a first logic value level to a second logic value level. In the solid-state laser device that controls the peak value of the Q-switched pulsed laser light that is oscillated and output from the device,
A reference pulse signal generating means for generating a reference pulse having a rectangular waveform having the repetition frequency and a constant pulse width;
A current mirror circuit having first and second transistors having respective control terminals commonly connected to each other;
Connected between a terminal of a first power supply voltage and the current mirror circuit, inputs the reference pulse, and conducts only for a time corresponding to the pulse width of the reference pulse, and then supplies the current mirror circuit to the first current mirror circuit. Switch means for supplying the power supply voltage of
A capacitor connected between a terminal of a second power supply voltage and the first transistor;
A current value variable type constant current source connected between the terminal of the second power supply voltage and the second transistor;
Current value selection means for selecting a current value of the constant current source to a desired value;
A discharging means for forming a closed circuit with the capacitor, allowing the capacitor to be charged only for a time corresponding to a pulse width of the reference pulse, and discharging the capacitor after the end of the time;
A solid-state laser device comprising pulse signal output means for outputting the voltage of the capacitor as the pulse signal.

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