Research On The Fabrication Technology Of Cylindrical Hologram Phase Grating With High Precision Used For Measuring

Cylindrical grating is widely used in stylus profiler as a kind of metrological grating. The requirement of large range and high resolution is posed with the ultra-precision machining technology developing towards sub-micron scale or even nanoscale. The cylindrical hologram phase grating is the standard of profile-meter and determines its resolution. The technical parameters and precision of cylindrical hologram phase grating directly affect the measurement accuracy and precision of stylus profiler.Combining with the application of cylindrical grating and the diffraction theory of grating, the errors coming from fabrication process of holographic grating and the influence of these technical parameters errors on precision are studied and comprehensively analyzed in this paper. The main contents and research results are as follows:(1) The working principle of cylindrical grating in surface measurement is analyzed. Thus, the relationship between the out-put signal and grating technical parameters is established.(2) The main technical parameters errors of grating such as periodic error, duty-cycle error, groove depth error and surface-shape error are analyzed based on scalar diffraction theory and RCWA theory of grating. The primary error sources(i.e. period error and duty-cycle error) which affect measurement accuracy and the corresponding process tolerances of them are clarified. This provides the theoretical basis for the fabrication of cylindrical grating with high precision.(3) A mathematical model about the density distribution and cumulative error in the holographic record of cylindrical grating is developed. For holographic record with plane waves, a novel fabrication method, i.e. the segmented exposure method which can improve the consistency of density distribution of cylindrical grating effectively is proposed. For holographic record with spherical waves, the cumulative error within the scope of whole range can be reduced to zero by optimization of the positions of point light in holographic record.