The Study Of Key Technologies In The Laser Beam Directional Stability System

The laser beam treated as a linear reference is used widely in the manufacture and measurement equipments, due to its many advantages, such as high brightness, good directivity, and good coherence etc. But the further improvement of the laser directional stability accuracy is restricted by some factors, such as the environment etc, which restrain the application greatly in the ultra-precision manufacture and measurement equipments. So adjusting the drift of laser beam and improving its directional stability, which is the key technology in the domain of the linear reference technology, demands to be solved.Based the research on the laser beam drift feedback control technique, analysing the beam drift and its frequency components, a laser beam directional stability method is studied in the thesis in detail, with its measurement and control circuit system that combines the laser beam intensity modulation and the beam drift feedback control technique. In this method, at first the laser beam intensity is modulated with the acoustooptic modulator, then the lock-in amplifier is applied to detect and demodulate the modulating signal, at last a feedback control signal is generated by the DSP control circuit at last, including:1. The detecting accuracy of the beam drift would be improved, as a high performance acoustooptic modulator modulates the frequency of the laser beam drift signal far away from the power frequency, the double power frequency and high frequency noises. It is quite important that the stability of signal's amplitude which is modulated by the acoustooptic modulator. The modulating signal is generated in the way of Direct Digital Synthesizer technology. The signal has many characteristics such as ultra wide frequency bandwidth, ultra high frequency resolution and ultra good phasic continuity, etc. Thus it can be achieved the high frequency and amplitude stability of the modulating signal.2. The thesis introduces the lock-in amplify technology to detect and demodulate the modulating signal from the noises, which can improve the SNR and provide a good signal for subsequent circuits disposed. Photoelectric detecting circuit is constituted of four parts, I/V conversion, lock-in amplifier, low-pass filter and operation.