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用基尔霍夫衍射公式分析反射式共焦光路 ,得到了被测件有一定倾斜角度表面的共焦轴向响应理论模型。由菲涅耳衍射近似公式得到的共焦轴向响应特性只是它的理论模型的一个特例。同时 ,对接收端采用差动连接的共焦测量的聚焦瞄准信号进行了分析 ,得到了表面倾斜角对聚焦瞄准信号影响的关系。应用共焦实验系统及差动测量系统对具有不同倾角的块规斜面的轴向响应信号进行了测量。理论模型的数值分析与实验结果相吻合。用差动共焦光学系统作为瞄准传感器、用电容传感器进行位移监测 ,对倾角为 10°的角规的斜面进行测量 ,得到分辨率小于 2 0nm的表面形貌图。
The Kirchhoff diffraction formula is used to analyze the reflection confocal optical path, and the theoretical model of the confocal axial response of the measured object with a tilted surface is obtained. The confocal axial response obtained from the Fresnel diffraction approximation formula is but one special case of its theoretical model. At the same time, the focusing aiming signal of the confocal measurement with differential connection at the receiving end is analyzed, and the relationship between the surface tilt angle and the focusing aiming signal is obtained. The confocal experimental system and the differential measuring system were used to measure the axial response signals of block slant with different inclination. The numerical analysis of the theoretical model is consistent with the experimental results. With the differential confocal optical system as the aiming sensor, the capacitance sensor was used to monitor the displacement. The bevel angle of the angle gauge of 10 ° was measured to obtain the surface topography with a resolution of less than 20 nm.