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In this paper, we suggest a polishing head with a mechanical gimbals-like structure for the optics fabrication. In the small tool polishing processes, several types of polishing mechanism have been tried to get more deterministic and high efficient optical fabrication. The conventional polishing processes to use the contacting pad material of polyurethane or pitch need the higher polishing rate to shorten the overall polishing time for large optics. Therefore, new polishing head mechanism is designed to use the air backpressure and gimbals-like hinge structure to increase polishing velocity. In the following experiment, mechanical adaptability was confirmed both on the flat glass and the convex aluminum surface.
In order to analyze the motion errors of the aerostatic stage, it is necessary to consider the influence of the moment variation occurred inside the pads. In this paper, a motion error anaysis method utilizing the transfer functions on the reaction force and moment is proposed, and general characteristics of the transfer functions are discussed. Calculated motion errors by the proposed method show good agreement with the ones calculated by Multi Pad Method, which is considered the entire table as an analysis object. Also, by the introduction of the transfer function of motion errors, which represent the relationship between the spatial frequency components of the rail form error and motion errors, motional characteristics of the porous aerostatic stage can be generalized. In detail, the influence of the spatial frequencies is analyzed quantatively, and the patterns of the insensitive frequencies which almost do not affect the linear motion error or angular motion error according to the rail length ratio and the number of the pad are verified. The relationship between the moment variation occurred inside the pads and the motion errors is also verified together.
The ultra precision machining in industrial field are increased day by day. The diamond turning has been used generally, but now is faced with limitation of use, because of higher requirement of production field. The electron beam lithography is alternative in machining area as semiconductor production. For EB lithography, 5 axis vacuum stage is required to duplicate small and large patterns on wafer. The stage is composed of 2 rotational axis and 3 translational axis with 5 DC servo motors. The positioning repeatability and resolution of Z axis feed unit are 3.21㎛ and 0.5㎛/step enough to apply to lithography.
The large optics in the telescope need an extreme level of both form accuracy and surface roughness such as sub-nanometer. To get the large optics of high quality surface, our strategic approach is to make a hybrid and complex machine with grinding, polishing, and measurement function. Therefore, the machine is being equipped with the ELID grinding and the computer-controlled polishing and the optics interferometer module to manufacture a large optics in short cycle. Its current goal is pursuing to acquire a large mirror optics of diameter 1.5m and final form accuracy is λ/10(50㎚) rms. In this paper to show our first result, we described machine design process by the error budget analysis and the conceptual arrangement of machine modules and machine structure and positioning performance was experimentally verified.