Research On Frequency Stabilization Of A Double Longitudinal He-Ne Laser By Digital Controll

With the development of science and technology, the requirement for the capability of large-size ultra-precision equipment becomes more and more strict, not only require ultra-precision measurement, but also fast. Thermal frequency stabilized laser with double longitudinal offers great characters, such as simple-structure, large beat frequency, well disturbance-resistant. It is widely used in fast ultra-precision laser heterodyne interferometry.The novel analyzes the double longitudinal laser principle and the reason that aroused the frequency floated, then according to the characteristic of frequency stabilization, design the scheme and strategy. As to solve the problem in the field of the process control on the laser, such as the complex of the control algorithm, the long time of warm-up , the low frequency repetition and the drifting in controller unit, the novel designs and realizes the warm up and control algorithm and the digital frequency stabilizing controller. The main tasks has been accomplish are following:(1) Digital controller based on DSP with 16bit analog input and output precision guaranteed is designed, and precision sampling of temperature, laser power difference and outputting of controlling signal are implemented. The novel also realize the controlling state outputting with the concentration line of RS232.(2) Operating system of the controller based on the UC/OS-II is introduced to facilitate the establishment of the controlling procedure of frequency stabilizing and multi-task switching, it make sense to actively debugging and utilizing the complex algorithm.(3) A temperature monitor circuit based on platinum resistance sensor is designed, it can be realized high precision measurement.(4) The warm up and stabilized model was analysised and established, then get the identification model of the system for the controller using the method of phase-step-response experiment.(5) Choose the proper algorithm as the warm up and stabilization algorithm, then give out the experiment results.According to the experiment result, using the strategy and the Digital controller presented by this paper, the time of warm-up of the laser is shorter than 15min, the frequency stabilization accuracy of the 10 seconds'sampling can get 10-10.