JP3445390B2 - Marking processing equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a marking processing apparatus using an acousto-optic Q switch. 2. Description of the Related Art FIG. 6 is a block diagram of a continuous-pumped Q-switched laser oscillation device. Nd-YAG
Is disposed, and the solid-state laser medium 2
, An excitation lamp 3 is arranged in parallel. On the longitudinal side of the solid-state laser medium 2,
A high-reflectance mirror 5 and an output mirror 6 constituting the laser resonator 4 are arranged. This laser resonator 4
An acousto-optic Q switch 7 (hereinafter, referred to as a Q switch element) is disposed inside, that is, between the high reflectance mirror 5 and the output mirror 6. The Q-switch element 7 performs a switching operation by using high-frequency power at an arbitrary repetition frequency supplied from a Q-switch drive circuit 8.
The excitation lamp 3 is supplied with a lamp voltage from an excitation lamp light source 9. With this configuration, when the excitation lamp 3 is turned on, the solid-state laser medium 2 is excited. The light emitted from the solid-state laser medium 2 by this excitation is converted into the solid-state laser medium 2
The laser beam passes through the mirror and reciprocates between the high-reflectance mirror 5 and the output mirror 6 to generate laser oscillation. In this state, the Q switch driving circuit 8
When high-frequency power as shown in FIG. 7 is supplied to the switch element 7, the optical loss in the laser resonator 4 increases during this high-frequency power supply, laser oscillation stops, and the solid-state laser medium 2 The population inversion within becomes larger. On the other hand, when the supply of high-frequency power from the Q switch drive circuit 8 to the Q switch element 7 is completely stopped, during this stop, the optical loss in the laser resonator 4 becomes zero, and laser oscillation occurs. At this time, the laser pulse output obtained by passing through the output mirror 6 is a pulsed laser beam having a high peak intensity because stimulated emission by a large population inversion is performed in a short time. As described above, in the Q switching method in which the high frequency power to the Q switch element 7 is completely stopped, the peak intensity of the laser pulse changes according to the magnitude of the population inversion in the solid-state laser medium 2 at that time. For this reason, when the repetition frequency of the Q switch element 7 changes, the magnitude of the population inversion in the solid-state laser medium 2 also changes according to the repetition frequency.
It is difficult to maintain the peak intensity of the laser pulse at a constant value with respect to the change in the repetition frequency of the Q switch element 7. Incidentally, a continuous excitation Q-switched laser oscillator having a high peak intensity has been widely applied to processing such as marking. In this marking processing, a method of scanning a Q-switch laser beam in accordance with a marking pattern is mainly used, and the following two points are very important from the viewpoint of processing finish. The first point is that the number of laser pulses applied to a workpiece becomes a constant value per unit length on a line to be marked. The second point is that the peak intensity of the irradiated laser pulse becomes constant. However, in actual marking, a high-speed scan is performed, so that the scan speed changes. Therefore, in order to keep the number of laser pulses per unit length constant, the number of repetitions of the Q-switch element is varied according to the scan speed. Fluctuates up to When the peak intensity of the laser pulse fluctuates in this way, it becomes a great obstacle to obtain a good finish in laser processing. [0014] As described above, when the number of repetitions of the Q switch element is changed, the peak intensity of the laser pulse also changes. Accordingly, it is an object of the present invention to provide a continuous excitation Q-switch laser oscillation method and apparatus capable of outputting a laser pulse maintained at a constant peak intensity even when the number of repetitions of the Q-switch element changes. [0015] In order to achieve the above object,
The invention corresponding to claim 1 includes a solid-state laser medium,
An excitation lamp for exciting a solid-state laser medium;
The light emitted from the medium is reciprocated into the solid-state laser medium and
Laser oscillator for generating laser oscillation and this laser oscillator
A Q-switch element disposed therein and the Q-switch element
At a repetition frequency of at least 1 kHz.
And Q switch driving means for performing a switching operation.
Alternating high frequency power and residual high frequency power for Q switch element
Marking processing equipment that is supplied periodically to
The repetition frequency changes even if the repetition frequency changes.
The peak intensity of the pulsed laser emitted from the oscillator
So that the residual high-frequency power is
It is configured to be supplied so as to monotonically decrease with the wave number
A marking processing apparatus characterized in that: According to the first aspect, the laser oscillation is generated in the laser resonator, and the Q disposed in the laser resonator.
When the switching element is repeatedly operated, the high frequency power supplied to the Q switching element is controlled in response to the repeated operation of the Q switching element, and a laser pulse having a constant peak intensity is obtained even if the number of repetitions of the Q switching element changes. Is output. An embodiment of the present invention will be described below with reference to the drawings. The same parts as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 1 is a configuration diagram of a continuous excitation Q-switched laser oscillation device. A Q switch drive circuit 10 is connected to the Q switch element 7. This Q switch drive circuit 10
Receives a repetition frequency signal of the Q-switch element 7 from the optical loss control circuit 11, and outputs a small high-frequency power (hereinafter referred to as a residual high-frequency power) corresponding to the repetition frequency when outputting a laser pulse. It has the function of supplying to Here, the process of calculating the residual high frequency power value will be described. The correspondence between the repetition frequency of the Q switch element 7 and the residual high frequency power was experimentally obtained by the following method. Using the repetition frequency of the Q-switch element 7 and the residual high-frequency power supplied from the Q-switch drive circuit 10 when outputting a laser pulse as parameters, the output laser pulse waveform is observed with an oscilloscope. The peak intensity of the laser pulse is read from the observed waveform, and the result is shown in FIG. That is, the peak intensity of the laser pulse with respect to the residual high-frequency power is 20 kHz, 10 kHz, 5 kHz, and 2 kHz at each repetition frequency.
z are shown as peak intensity curves A to E for each 1 kHz. From the result of the peak intensity of the laser pulse, when the value of the peak intensity i of the laser pulse is held,
The corresponding relationship to be satisfied between the repetition frequency of the Q switch element 7 and the residual high-frequency power is obtained by taking the intersection of the peak intensity i and each of the peak intensity curves A to E. FIG. 3 shows the correspondence between the repetition frequency and the residual high frequency power. Accordingly, the Q-switch drive circuit 10 receives the repetition frequency signal of the Q-switch element 7 from the optical loss control circuit 11, and converts the residual high-frequency power corresponding to this repetition frequency to the repetition frequency and the residual high-frequency power shown in FIG. It has a function of supplying this residual high-frequency power to the Q switch element 7 when outputting a laser pulse. Next, the operation of the above-configured device will be described. When the excitation lamp 3 is turned on, the solid-state laser medium 2 is excited. This excitation causes the solid-state laser medium 2
Is transmitted through the solid-state laser medium 2 and reciprocates between the high-reflectance mirror 5 and the output mirror 6 to generate laser oscillation. In this state, the Q switch driving circuit 8
For example, as shown in FIG.
When the high-frequency power of W is supplied, the optical loss in the laser resonator 4 increases during the supply of the high-frequency power, the laser oscillation stops, and the population inversion in the solid-state laser medium 2 increases. On the other hand, the optical loss control circuit 11 converts the repetition frequency signal of the Q switch
Has been sent to Therefore, in the next cycle, the Q switch drive circuit 8 receives the repetition frequency signal from the optical loss control circuit 11, finds the residual high frequency power corresponding to the repetition frequency from the correspondence shown in FIG. It is supplied to the Q switch element 7. That is, the power supplied to the Q switch element 7 switches from a high frequency power of 70 W to a minute residual high frequency power corresponding to the repetition frequency. When the power supplied to the Q switch element 7 is switched to the residual high frequency power, the optical loss in the laser resonator 4 decreases,
A laser oscillation state is set. Accordingly, a laser pulse is output from the laser resonator 4. Since the residual high-frequency power at this time is controlled to a power amount corresponding to the repetition frequency of the Q switch element 7, the peak intensity of the output laser pulse is Q
It has a constant value irrespective of the change in the repetition frequency of the switch element 7. FIGS. 5 (a) to 5 (c) show the case where the repetition frequency of the Q switch element 7 is 1 kHz, 5 kHz and 10 kHz.
3 shows a pulse waveform of a laser pulse. It can be seen from these pulse waveforms that the peak intensity of the laser pulse is maintained at a constant value even when the repetition frequency of the Q switch element 7 changes. As described above, in the above-described embodiment, when outputting the laser pulse, the minute residual high-frequency power corresponding to the repetition frequency is supplied to the Q switch element 7, so that the optical loss in the laser resonator is reduced. Is adjusted, and a laser pulse having a constant peak intensity can be output even if the repetition frequency of the Q switch element 7 changes. The change of the peak intensity of the laser pulse is as follows.
As shown in FIG. 2, the correspondence between the repetition frequency of the Q switch element 7 and the residual high frequency power shown in FIG. 3 is obtained by taking the intersection of the peak intensity i of the desired laser pulse and each of the peak intensity curves A to E. If this correspondence is held in the Q switch drive circuit 10, this can be easily realized. Therefore, a laser pulse having a constant peak intensity can be output even if the repetition frequency of the Q-switch element 7 changes. Therefore, in laser processing, two important points for obtaining a good processing finish, that is, the first point, The second point satisfies that the number of laser pulses applied to the object has a constant value per unit length on the line to be marked, and the second point is that the peak intensity of the applied laser pulse is constant. The present invention is not limited to the above embodiment, but may be modified as follows. For example, the high frequency power supplied to the Q switch 7 may detect the peak intensity of the output laser pulse and perform feedback control so that the peak intensity is maintained at a constant value. As described above in detail, according to the present invention, Q
Even if the number of repetitions of the switching element changes, a marking device that can output a laser pulse with a constant peak intensity
We can provide a processing device .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing one embodiment of a marking processing apparatus according to the present invention. FIG. 2 is a diagram showing a relationship between a residual high frequency power supplied to a Q switch element of FIG . 1 and a pulse heater intensity. FIG. 3 is a diagram showing a relationship between a repetition frequency and a residual high-frequency power of the Q switch element of FIG . 1 ; FIG. 4 is a diagram showing residual high-frequency power supplied to the Q switch element of FIG . 1 ; FIG. 5 is a diagram showing a laser pulse waveform having a constant peak intensity in FIG . 1 ; FIG. 6 is a configuration diagram of a conventional device. FIG. 7 is a diagram showing high-frequency power supplied to the Q switch element in FIG . 6 ; [Description of Signs] 2 ... solid laser medium, 3 ... excitation lamp, 4 ... laser resonator, 5 ... high reflectivity mirror, 6 ... output mirror, 7 ... acousto-optic Q switch, 10 ... Q switch drive circuit, 11 ... Light loss control circuit.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01S 3/00-3/30

Claims (1)

(57) [Claim 1] A solid- state laser medium, an excitation lamp for exciting the solid-state laser medium, and radiated light from the solid-state laser medium in the solid-state laser medium.
A laser oscillator that reciprocates to generate laser oscillation, a Q-switch element disposed in the laser oscillator, and a repetition of the Q-switch element of at least 1 kHz or more.
Q-switch drive for switching operation according to frequency
Means and high frequency power and residual
High-frequency power is supplied alternately and periodically.
In the marking processing device, even if the repetition frequency changes, the laser oscillator
Make the peak intensity of the emitted pulse laser constant
The residual high frequency power is
That the supply is monotonically decreasing
Characteristic marking processing equipment .