Waveness Profilometer of Large Optical Parts Insensitive to the Waveness and Roughness of Reference Mirror

研制了一种适用于大型超光滑表面的仿形仪，在均方根约为0.4 gal的振动环境下，其高度灵敏度为0.1 nm。在获取轮廓时，以恒定速率在表面上扫描测量点。干涉测量系统继续测量目标点与其周围环境之间的高度差。在测量过程中使用参考镜中的相同部分，则镜子的粗糙度不会影响测量数据。差分高度具有高空间频率分量的衰减强度。然而，数字信号处理可以恢复原始强度的组件，除了一个特征参数，曲率半径的表面。该半径可以从该仪器对具有已知绝对轮廓的另一个大的光滑表面测量的数据来评估。

A profiling instrument is developed for large supersmooth surfaces, which has a height sensitivity of 0.1 nm under vibrational environments of approximately 0.4-gal root mean square. In taking a profile, a measurement point is scanned on a surface at a constant rate. An interferometric system continues to measure a differential height between the aimed point and its surroundings. The same part in a reference mirror is used during the measurement, then the roughness of the mirror does not affect the measured data. The differential height has the attenuated intensities for high spatial-frequency components. However, a digital signal processing can retrieve the original intensities of the components except one characteristic parameter, the radius of curvature of the surface. This radius can be evaluated from the data which have been measured by this instrument for another large smooth surface having a known absolute profile.