The edge roll off seriously restricts the further improvement of the overall surface figure accuracy in CP of large planar optics. Firstly, the half width and depth of large planar optics’ edge region is proposed to quantify the roll off degree by analyzing its radial equivalent profile. Then, a two-dimensional symmetrical model of the large planar optics and the pitch lap is established. Next, based on the finite element model, the influence of extension block’s bonding state on the large planar optics edge’s stress concentration is analyzed. Finally, the effectiveness of this proposed method is verified by CP of large planar optics with extension blocks.
Continuous polishing is a significant process to fabricate optical workpiece with nano figure precision. The figure of the optical workpiece is to a large extent dependent on the surface shape of the pitch lap. In this study, a novel method is proposed to determine the lap shape error by moving the measurement point in a generally radial direction while the lap rotates and correct the lap shape error by employing a small heat tool considering its viscoelastic property. It is validated that the surface shape error of the pitch lap can be corrected dramatically by the method, and the workpiece figure attempts to target the lap shape so as to reach a uniform material removal.
The pressure distribution is the most vital to material removal in continuous polishing in which removes the scratches and subsurface damage induced in grinding and lapping. Firstly, the interface response mechanism of the static contact pair is determined by uniaxial compression test. Then, the numerical model of the optics (Φ50mm×5mm ) and polishing lap(Φ80mm×7mm) contact pair is established to acquire the pressure distribution based on elastic contact mechanics. After that,the compression behavior is characterized by the pressure distribution and real contact area (RCA) measured by fujing pressure film. Attempt is made to clarify the figure of optics in continuous polishing.
The principle of measuring displacement by eddy current sensor was derived. The calibration experiment was carried out for 5 kinds of different materials, which showed that the linearity of eddy current sensor was better, and the sensitivity of eddy current sensor varied with different materials. Based on the principle of measuring displacement by eddy current sensor, the on-line detection system for diamond circular wheel was designed, and the data acquisition was realized by using LABVIEW software. By moving the eddy current sensor in the vertical direction with the grinding wheel fixed, the coordinate of arc in the grinding wheel was obtained. The radius of the grinding wheel was fitted by using the genetic algorithm, which showed that the fitting results were accurate. The data acquisition of the grinding wheel was carried out in a cycle by fixing the electric eddy current sensor and the circulars of the grinding wheel in different processes, namely before dressing, after dressing and after shaping. The results showed that the circular of the grinding wheel after dressing and after shaping were significantly improved compared with that before dressing.
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