The present invention relates to a gas laser oscillator equipped with a constant laser gas pressure system which controls the laser gas pressure to be constant by exhausting and supplying certain amount of laser gas.
FIG. 3 shows outline structure of a conventional gas laser oscillator including a constant laser gas pressure system. In the following, a conventional method for controlling the laser gas pressure constant in a gas laser oscillator is described with reference to FIG. 3.
A conventional gas laser oscillator with constant laser gas pressure system comprises a power supply 1 for laser gas excitation by a discharge, a laser gas chamber 2, a vacuum pump 3, a laser gas bottle 4, an electromagnetic valve 5 for laser gas supply, a laser gas pressure sensor 6 for detecting the laser gas pressure within the laser gas chamber 2 and a laser gas pressure controller 7 which opens/closes (i.e performs open-and-close actions) the electromagnetic valve 5 for laser gas supply in order to maintain the pressure constant by comparing the signals detected by the laser gas pressure sensor 6 with a reference value.
The above-description illustrates structure of the constant laser gas pressure system of a conventional gas laser oscillator; in the following, operation of the system is described.
As a general rule among the gas laser oscillators, it is essential to keep laser gas pressure within the laser gas chamber 2 connected with the excitation power supply 1 constant, in order to maintain a stable laser output. Also, in order to prevent decrease of the decrease of output power due to deterioration of the laser gas, new laser gas is supplied continuously, or intermittently, from the laser gas bottle 4 or the like means connected with the gas laser oscillator.
The vacuum pump 3 connected to the laser gas chamber 2 exhausts deteriorated laser gas out of the laser gas chamber 2 as the routine work. When laser gas is exhausted the pressure of laser gas within the laser gas chamber 2 drops, and then the electromagnetic valve 5 for laser gas supply is opened to supply new laser gas into the laser gas chamber 2 from the laser gas bottle 4 connected to the gas laser oscillator. Quantity of the exhaust and that of the supply need to be well balanced; otherwise the pressure within the laser gas chamber 2 can not be kept constant. In order to keep the pressure constant, the laser gas pressure sensor 6 connected to the laser gas chamber 2 detects laser gas pressure within the laser gas chamber 2 and transmits signals of detected results to the laser gas pressure controller 7. The laser gas pressure controller 7 compares the signals of detected results with a reference value, or target value for the laser gas pressure, and opens/closes the electromagnetic valve 5 so that the laser gas pressure is maintained constant. The cycle period of open/close actions is kept stable when a gas laser oscillator is working normally.
The above-configured conventional gas laser oscillator has following drawbacks.
After a long operation period, a gas laser oscillator sometimes exhibits a sudden drop in the laser output, or stops, due to leakage caused by a deteriorated vacuum seal or the like of the laser gas chamber 2 (hereinafter referred to as xe2x80x9cvacuum leakxe2x80x9d). In most of the cases, the vacuum leak does not take place abruptly, but it starts from a micro leak which hardly affects the laser output and it gradually develops into a leak that matters. Therefore, if the micro leak is detected at an early stage, a certain preventive maintenance measures can be taken to avoid such drop of laser output. Measurement of the vacuum leak has been conducted during the time when a gas laser oscillator is out of duty, using a measuring equipment. Lately, an increasing number of gas laser oscillators are put into operation continuously around the clock. On the other hand, there has been no effective means for detecting the micro vacuum leak applicable to gas laser oscillators at work. Once a sudden drop of laser output actually happens, scheduled maintenance is hardly helpful; in addition, the gas laser oscillator that is out of order is put aside for a considerable length of time before it is repaired. Thus, the inconvenience spreads over a production floor related to the processing with gas laser.
The present invention addresses the above-described problems.
A gas laser oscillator of the present invention comprises:
a power supply for exciting laser gas by a discharge;
a laser gas chamber for containing the laser gas;
means for exhausting laser gas contained in the laser gas chamber;
a gas pressure sensor for detecting gas pressure in the laser gas chamber;
an electromagnetic valve for supplying laser gas into the laser gas chamber from a gas bottle so that pressure of the laser gas as detected by the gas pressure sensor is maintained constant;
detection means for detecting deviation in a cycle period of open/close actions of the electromagnetic valve from a reference value; and
an alarm display controller for issuing an alarm based on a detection results delivered from the detection means.
A gas laser oscillator of the present invention is also provided with a stop controller, which suspends the excitation of laser gas discharge in a case when the cycle period of open/close actions of the electromagnetic valve becomes longer than a reference value.