JPH0119407Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a solid-state laser oscillation device that prevents the output of laser light from becoming unstable due to the temperature of the laser rod not being constant.

[Technical background of the invention and its problems]

Generally, in a solid-state laser oscillator, the laser rod is optically pumped with an excitation lamp.
When the temperature of this laser rod changes, the output of the laser beam becomes unstable, leading to a decrease in oscillation efficiency. Therefore, a circulation path through which a cooling medium circulates is formed in the solid-state laser oscillator, so that the laser rod is cooled by the cooling medium.

Conventionally, the temperature of the laser rod has been controlled by circulating a certain amount of cooling medium through a circulation path, detecting the temperature of the cooling medium, and using this detection signal to maintain the temperature of the cooling medium constant. However, when the laser rod is pulse-excited by an excitation lamp in order to pulse the laser beam,
Since the laser rod's temperature rises rapidly, simply circulating a certain amount of temperature-controlled cooling medium has low cooling efficiency and it takes a long time for the laser rod to drop to a predetermined temperature. Therefore, there was a problem in that a laser beam with unstable output was oscillated for a long time.
Furthermore, if the laser rod is made of beryllium aluminate doped with chromium ions, the pulse repetition rate can be increased compared to a laser rod made of ruby. Therefore, since the difference between the maximum and minimum pulse intervals becomes large, the temperature change of the laser rod also increases in accordance with the difference in the pulse intervals, causing a problem that the instability of the output becomes even more pronounced.

[Purpose of invention]

This invention directly detects the temperature of the laser rod, and uses this detection signal to change the flow rate of the cooling medium to control the temperature of the laser rod, making it possible to keep the temperature of the laser rod constant more quickly than before. The object of the present invention is to provide a solid-state laser oscillation device that achieves the following.

[Summary of the idea]

The temperature of the laser rod is detected by a detector,
This detection signal is used to control the flow rate of the cooling medium circulating through the circulation path using a control valve, thereby changing the cooling capacity of the cooling medium in response to changes in the temperature of the laser rod, making it possible to quickly bring the laser rod to a constant temperature. This is what I did.

[Example of idea]

An embodiment of the present invention will be described below with reference to the drawings. In the figure, 1 is the main body of the laser oscillation device. Inside the main body 1, there is provided a condensing and reflecting mirror 2 which has a cylindrical shape and has a mirror-finished inner peripheral surface. A laser rod 3 made of, for example, beryllium aluminate doped with chromium ions, and an excitation lamp 4 for optically exciting the laser rod 3 are inserted along the axial direction of the converging reflector 2 and are spaced apart from each other. ing. The laser rod 3 is held by a pair of cylindrical holders 5, each of which has one end fitted in a liquid-tight manner and the other end protruding from both sides of the main body 1 in a liquid-tight manner. A pair of reflecting mirrors 6, 6 constituting a resonator are arranged in parallel at the openings at the other ends of the holders 5, 5, and a laser beam L is output from one of the reflecting mirrors 6. Furthermore, a filter 7 is provided between the laser rod 3 and the excitation lamp 4 for removing wavelength components harmful to laser oscillation from the excitation light from the excitation lamp 4.
is provided.

The main body 1 has an inlet 8 and an outlet 9 formed therein. A supply pipe 11 equipped with a pump 10 is connected to the inlet 8 , and a return pipe 12 is connected to the outlet 9 .
The return pipe 12 and the return pipe 12 communicate with a liquid storage tank 13. A cooling medium L (for example, water) is stored in this liquid storage tank 13, and when the pump 10 is operated, it returns to the liquid storage tank 13 from the supply pipe 11 through the main body 1 and the return pipe 12. It circulates. By passing through the main body 1, the laser rod 3 and excitation lamp 4 are cooled. Further, the supply pipe 11 and the return pipe 12 are connected by a bypass pipe 15 having a first control valve 14 in the middle. The first control valve 14 is connected to a first detector 1 which is made of a thermocouple or thermistor heat-sensitive element, which is connected to the outer surface of one end of the laser rod 3.
The opening and closing of the laser rod 6 is controlled as described later in accordance with the temperature of the laser rod 3 detected by the laser rod 6. The first detector 16 is covered with a cover 17 to prevent it from malfunctioning due to the excitation light from the excitation lamp 4.

Further, a lead wire 18 connected to the first detector 16 is led out through the return pipe 12 and the liquid storage tank 13, and is connected to the first amplifier 19. A synchronous detection circuit 20 and a second amplifier 21 are sequentially connected to the first amplifier 19 , and the second amplifier 21 is connected to a first comparator 22 . A first setter 23 is connected to the first comparator 22, and the set value from the first setter 23 is compared with the temperature of the laser rod 3 detected by the first detector 16. Ru. When the temperature of the laser rod 3 is higher than the set value, a signal from the first comparator 22 causes the first control valve 14 provided in the bypass pipe 15 to be closed.

Further, a power source 24 is connected to the excitation lamp 4, and the power source 24 is driven by a pulse signal from a pulse generator 25 to supply power to the excitation lamp 4 in a pulsed manner. The pulse signal from the pulse generator 25 is also input to the synchronous detection circuit 20 as a synchronous signal via the synchronous waveform generation circuit 26. This synchronization signal turns ON when the pulse signal is not output from the pulse generator 25, and turns OFF when the pulse signal is output. The synchronous detection circuit 20 is configured to allow the detection signal from the first detector 16 to pass through by the signal from the synchronous waveform generation circuit 26 only when the synchronous signal is ON. That is, from the pulse generator 25 as shown in FIG.
When the pulse signal is output as shown in FIG. 2b and the excitation lamp 4 is lit as shown in FIG.
As shown in , the synchronization signal is output only when the excitation lamp 4 is not lit. Therefore, the detection signal from the first detector 16 is not affected by the noise generated when the excitation lamp 4 outputs excitation light, so that the temperature of the laser rod 3 can be accurately measured. Become.

On the other hand, the liquid storage tank 13 is provided with a heat exchanger 27. Cold water for cooling the cooling medium L is circulated through the heat exchanger 27, and a second control valve 28 is provided on the inflow side where the cold water flows into the heat exchanger 27. . Also,
The liquid storage tank 13 is provided with a second detector 29 that detects the temperature of the cooling medium L therein. The detection signal from this second detector 29 is
The signal is input to a second comparator 31 via an amplifier 30. This second comparator 31 includes a second setter 3.
2 is connected, and the set value from this second setter 32 and the temperature of the cooling medium L, which is a detection signal from the second detector 29, are compared. If there is a difference between the comparison values, the second control valve 28 is controlled to open or close by the signal from the second comparator 31. That is, when the temperature of the cooling medium L rises, the second control valve 28 is opened to allow cold water to flow into the heat exchanger 27, and conversely, when the temperature of the cooling medium L is below the set value of the second setting device 32, In some cases, the second
control valve 28 is closed. Therefore, the temperature of the cooling medium L is kept constant by the heat exchanger 27.

Note that the temperature set for the cooling medium L by the second setter 32 is lower than the temperature set for the laser rod 3 by the first setter 23.

Next, the operation of the above configuration will be explained. When the temperature of the laser rod 3 is lower than the set value set by the first setter 23, the first comparator 2
2 to the first control valve 14, this first control valve 14 is open. Therefore, a part of the cooling medium L circulated by the operation of the pump 10 passes through the bypass pipe 15 and reaches the liquid storage tank 1.
Bypassed to 3.

In this state, when the laser rod 3 is optically excited by the excitation lamp 4 and its temperature rises rapidly, this is detected by the first detector 16. The detection signal from the first detector 16 passes through the synchronous detection circuit 20 in response to the synchronous signal from the synchronous waveform generation circuit 26, is input to the first comparator 22, and is output from the first setter 23. Compare with set value. Then, when the temperature of the laser rod 3 is higher than the set value by the first setting device 23, the first comparator 22 sends a signal to the first control valve 14.
A signal is issued to close the first control valve 14 and cut off the bypass pipe 15. Then, since the cooling medium L that had previously bypassed the bypass pipe 15 also flows into the main body 1, the flow rate of the cooling medium L circulating within the main body 1 increases. Therefore, the laser rod 3 is rapidly cooled to a predetermined temperature by increasing the flow rate of the cooling medium L. Furthermore, since the controlled temperature of the cooling medium L is lower than the temperature set for the laser rod 3 by the first setting device 23, the cooling speed of the laser rod 3 is increased.

In the above embodiment, the case where the laser beam is oscillated in pulses has been described, but according to the present invention, the temperature of the laser rod can be stabilized even when the laser beam is oscillated continuously. Further, the cooling medium may be used in separate paths for cooling the laser rod and the excitation lamp. For example, if the laser rod and the excitation lamp are inserted into transparent pipes and the cooling medium is passed through each pipe, the paths can be separated, and the cooling medium is guided through the pipes, making it smooth. circulate. moreover,
The laser rod may be made of other materials such as ruby.

In addition, in order to control the flow rate of the cooling medium in the present invention, a control valve whose opening degree is proportionally controlled is provided in the inflow pipe communicating with the liquid storage tank, excluding the bypass pipe, and
This may be done by controlling the opening degree of the control valve in accordance with the temperature change of the laser rod.

[Effect of idea]

As described above, the present invention directly detects the temperature of the laser rod using a detector installed in contact with the surface of the laser rod without being affected by the heat of the excitation lamp, and uses this detection signal to cool the laser rod. The flow rate of the cooling medium is now controlled. Therefore, when the laser rod is optically excited and its temperature rises rapidly, this is detected by the detector, and the detection signal increases the flow rate of the cooling medium that cools the laser rod.
The laser rod can be quickly cooled to a predetermined temperature compared to the conventional method in which the laser rod is cooled with a fixed amount of cooling medium. That is, by detecting the surface temperature of the laser rod, the temperature of the laser rod can be controlled with excellent responsiveness.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with Fig. 1 showing the overall configuration, and Figs. 2 a to c showing the lighting of the excitation lamp,
FIG. 3 is an explanatory diagram showing a relationship with a synchronization signal output at that time. 3... Laser rod, 4... Excitation lamp, 14
...First control valve, 15... Bypass pipe, 16...
...First detector, L...Cooling medium.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A laser rod, an excitation lamp for optically exciting the laser rod, a circulation path through which a cooling medium circulates to cool the laser rod and the excitation lamp, and a detector for detecting the temperature of the laser rod. and a control valve that controls the flow rate of the cooling medium circulating in the circulation path based on the detection signal from the detector, and the detector is configured to operate the laser rod in a state where it is not affected by the heat of the excitation lamp. A solid-state laser oscillation device characterized by being provided in contact with a surface. (2) The solid-state laser oscillation device according to claim 1, wherein the circulation path is provided with a bypass path, and the bypass path is provided with a control valve. (3) The solid-state laser oscillation device according to claim 1, wherein the temperature of the laser rod is detected by a detector in synchronization with a pulse signal input to an excitation lamp.