| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 107 === In this study, a recurring-diffraction grating interferometer for multi-degree-of-freedom measurement is proposed. The recurring-diffraction type grating interferometer is developed by combining the advantages of heterodyne interferometry, grating interferometry, recurring diffraction optical configuration, as well as the coplanar detection technique. It has the capability of measuring in five degrees-of-freedom (DOF) with high resolution and stability.
The proposed system takes advantage of a “recurring-diffraction” optical configuration, which directs diffracted light to pass through a grating twice without additional optical components, thereby doubling the phase change induced by grating displacement, effectively improving the resolution of the grating interferometer. In addition, the generally grating interferometer needs to increase the detection structures in each axial, or select a two-dimensional grating to achieve multi-dimensional measurement. Furthermore, the
This innovative recurring-diffraction interferometer through the incorporation of two optical
component. Three detection points are formed on the system, so that the system has the precision measurement capability of five degrees of freedom (x, z, θx, θy, θz) with few optical components, and has the advantages of no defocus detection and high light utilization rate, and successfully overcome the problem of grating interferomter multi degree of freedom in nowadays.
In order to verify the feasibility and performance of the proposed recurring-diffraction grating interferometer, a series of experiments were conducted, with the measurement results obtained from the proposed system compared with the built-in capacitive sensor and linear encoder of commercial positioning stages. As displayed in the results, the proposed recurring-diffraction grating interferometer has the ability to perform precision displacement and rotation measurement in five DOFs simultaneously without needing to change the optical configuration with resolutions for displacement and rotation measurement of 3 nm and 100 nrad, and the repeatability better than 0.62 nm and 63 nrad, respectively. The maximum velocity for displacement measurement can reach 160 μm/s. The proposed grating interferometer has excellent measurement properties, and is well-suited for applications within precision manufacturing, tool machine industry, automatic optical measurement, nanotechnology, semi-conductor technology and other related fields.
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