Visible light and infrared light, included in a femtosecond laser tracker, have been widely employed for precise orientation and high-precision ranging measurements of targets, respectively. In the above measurement process, it is always necessary to ensure the coaxiality of those two laser beams with different wavelengths. According to the structural characteristics of the instruments, a calibration method for the coaxiality of tracking light and femtosecond ranging light of the femtosecond laser tracker based on frequency doubling crystal is proposed, which is the detection of the coaxiality deviation caused by the included angle between the beams. We investigate the principle of two-beam laser coaxiality detection and calculate the parameters of the system. The detection system is further developed, and the error analysis is carried out. The results demonstrate that the tracking laser and femtosecond laser is coaxial within an accuracy of 1.5 arc sec, satisfying the measurement requirements.
A complete theory is established for opto-mechanical systems design of the window in this paper, which can make the design more rigorous .There are three steps about the design. First, the universal model of aerodynamic environment is established based on the theory of Computational Fluid Dynamics, and the pneumatic pressure distribution and temperature data of optical window surface is obtained when aircraft flies in 5-30km altitude, 0.5-3Ma speed and 0-30°angle of attack. The temperature and pressure distribution values for the maximum constraint is selected as the initial value of external conditions on the optical window surface. Then, the optical window and mechanical structure are designed, which is also divided into two parts: First, mechanical structure which meet requirements of the security and tightness is designed. Finally, rigorous analysis and evaluation are given about the structure of optics and mechanics we have designed. There are two parts to be analyzed. First, the Fluid-Solid-Heat Coupled Model is given based on finite element analysis. And the deformation of the glass and structure can be obtained by the model, which can assess the feasibility of the designed optical windows and ancillary structure; Second, the new optical surface is fitted by Zernike polynomials according to the deformation of the surface of the optical window, which can evaluate imaging quality impact of spectral camera by the deformation of window.
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