Theory Study On Accelerated Life Test Of He-Ne Lasers

In this paper, the approach used for accelerated life test under constant stress of mini He-Ne lasers with glass framework of 250mm is proposed to estimate its lifetime, in which theoretical research has been mainly discussed. According to the failure mechanism of He-Ne lasers working under normal conditions, we choose electric current as the accelerated stress of our test. The theoretical and experimental results show that the operating lifetime distribution of He-Ne lasers under normal working electric current and accelerated electric current both obey Weibull function. When the accelerated electric current is no more than 20mA, shape parameter m is basically the same; major changes of m will occur if the condition is converse, but the lifetime distribution still obey Weibull function. It is noted from this phenomenon that when the working electric current exceeds a certain value, new failure factors will appear.The electric current we choose in the test is higher than the value adopted in the normal accelerated life test. In order to estimate the lifetime of He-Ne lasers working under normal conditions, we amended the lifetime under big electric current and got the mathematical model for calculating the lifetime of He-Ne lasers. The feasibility of this method has also been discussed based on the analysis of experimental data. Moreover, the maximum flow of the accelerated electric current has been confirmed.In order to shorten test time further and reduce the number of tested tubes, a new approach used for treat experimental data named mixed with fix number and fix timing censored test method was proposed. That is, we used fix number censored test method under the accelerated electric current of 4I0(I0: electric current under normal working conditions), and then we used fix timing censored test method under the accelerated electric current of 3I0 and 2I0. Meanwhile, based on methods of Bayes estimation, maximum likelihood and the best linear undistorted estimation, the lifetime of He-Ne lasers working under normal conditions could be conveniently estimated. The approach can also be used for life test of other lasers (such as gas laser with ring cavity) and electronic components.