A feasible way to improve the manufacturing efficiency of large reaction-bonded silicon carbide optics is to increase the processing accuracy in the ground stage before polishing, which requires high accuracy metrology. A swing arm profilometer (SAP) has been used to measure large optics during the ground stage. A method has been developed for improving the measurement accuracy of SAP using a capacitive probe and implementing calibrations. The experimental result compared with the interferometer test shows the accuracy of 0.068 μm in root-mean-square (RMS) and maps in 37 low-order Zernike terms show accuracy of 0.048 μm RMS, which shows a powerful capability to provide a major input in high-precision grinding.
The swing arm profilometer (SAP) has been playing a very important role in testing large aspheric optics. As one of most significant error sources that affects the test accuracy, misalignment error leads to low-order errors such as aspherical aberrations and coma apart from power. In order to analyze the effect of misalignment errors, the relation between alignment parameters and test results of axisymmetric optics is presented. Analytical solutions of SAP system errors from tested mirror misalignment, arm length L deviation, tilt-angle θ deviation, air-table spin error, and air-table misalignment are derived, respectively; and misalignment tolerance is given to guide surface measurement. In addition, experiments on a 2-m diameter parabolic mirror are demonstrated to verify the model; according to the error budget, we achieve the SAP test for low-order errors except power with accuracy of 0.1 μm root-mean-square.
The high precision optical mirrors are quite important for the modern optical system. In this paper, a novel
Magnetic Medium Assistant Polishing technology and device is researched for optical finishing. The key element of the
device is a designed magnetic wheel and accessorial magnetic component. The solid magnetic powder arranged with the
magnetic field distribution and became a flexible polishing brush tool. The solid magnetic medium tool working with a
high rolling speed and the polishing liquid with abrasive was injected to contact region of the optical surface. The
magnetic powder tool is reforming with the magnetic field all the time, and this feature made the removal rate and
distribution of the removal function invariable. The device is connected to the polishing machine. The fabrication
experiments were completed. The distribution of the removal function is like a raindrop and asymmetry in one
orientation. The removal stability of the tool was quite good and achieves 95% sameness of peak value in one hour. The
primary experiments shown that the technology can be used in the practical fabrication.
Freeform surfaces provide more degrees of freedom for design of optical systems, and enhance the ability of
compensation and correction aberrations. Freeform surfaces are of advantage to balance the unsymmetrical aberrations, especially for the wide-field off-axis optical systems. This paper focus on an off-axis reflective optical system, which focal length is 550mm, F# is 6.5 and field of view (FOV) is 76°. The system adopts some freeform surfaces. We discuss the problems we noticed in processes of design, manufacture, measurement and alignment, and the solutions. At last, the periodical research result and the expected performance are given.
Laser chaotic system is used to complete private communication experiment in this paper. In the process of private communication, both chaotic laser beam and electric chaos signal which contain private signals are transferred to the place where the signals is received. Two same non-linear electric circuits with same response behavior are used in the experiment setup to change frequencies and waves of laser chaotic signal and electrical chaotic signal at the
same time. Even if both laser chaotic signal and electric signal are lost, transferred private signals are still safe.
Response of Bragg acousto-optic bistable system to external rectangular wave signals has been studied in this paper. When there is not external signals, the system is set up into stable state, and external signals are input into the system, response waves are observed on the bottoms of rectangular waves of external signals. As bifurcation parameters are changed, bifurcation and chaos are observed
in the response waves of the system.