Research On Miniaturized High-resolution Displacement Sensor Based On Self-imaging Effect Of Optical Gratings

With the improvement of displacement detection requirements for applications such as precision machinery manufacturing and high-performance semiconductor device processing,the demand for high-performance micro-displacement sensors in fields such as ultra-precision machining and measurement is becoming more and more urgent.Aiming at the urgent demand for integrated precision displacement sensors in precision machining/detection systems such as precision machine tools,lithography platforms,and electron microscopes,an in-plane displacement sensor based on two micro-gratings is proposed.Based on the self-imaging effect of micro-gratings,high performance(0.65 nm resolution)displacement measurement is realized combined with precision four-quadrant photo-detecting technology.Benefitting from excellent properties including high resolution,simple light path,and compact structure,the sensor shows great potential in applications such as precise positioning of the lithography machine workpiece table and ultra-precision machining machine tools.In order to complete the research of this sensor,the main research contents of this article are as follows:In the first chapter,by analyzing the measurement methods of several mainstream displacement sensors at this stage,and comparing the core indicators of displacement measurement such as resolution,linearity,and anti-interference ability,the technical characteristics and application advantages of the grating displacement sensor are summarized.According to the research and analysis of grating displacement sensors at home and abroad in recent years,the technical bottleneck of this type of sensor is summarized,and a new method using the self-imaging effect of grating is proposed to be used in the design of high-resolution and miniaturized displacement sensors.In the second chapter,based on Fourier optics and other theories,the diffraction characteristics of single layer gratings as well as the self-imaging effect of gratings are studied.The excitation conditions of the effect are analyzed.And the spatial light field distribution characteristics are characterized.Based on the grating self-imaging effect,a double-grating inplane displacement detection scheme is proposed,and a theoretical model of displacement detection is established.In the third chapter,based on the principle of grating self-imaging displacement detection,the overall structure of the double layer grating in-plane displacement sensor is designed,and the key indicators of the sensor are designed and analyzed.The optimal structural parameters such as the grating size and assembly requirements is obtained by a FDTD simulating process of the double-layer grating structure.The design of the double grating displacement detection module is completed.Combined with the grating parameters and structure distribution,the fabricating process of the micro-gratings is discussed.And the micro--gratings are fabricated successfully.In the fourth chapter,the whole sensor is designed and the experimental system is built.In the experiment,combined with high-precision photoelectric detection technology,four-way quadrature sine and cosine signal output are realized,and the displacement detection resolution of the sensor is improved by an electronic subdivision technology.The final experiment shows that the resolution of the in-plane displacement sensor can reach 0.65 nm with a maximum range of 500μm.Then,the source of the error is analyzed and an improvement scheme is proposed.Compared with the traditional grating displacement detection technology,the method features with a simple optical path and compact structure,which show great potential in applications such as miniaturization and integration of displacement detection devices and systems.In the fifth chapter,the research process of this paper is summarized and prospected.Through the analysis of the specific content,the measurement performance of the sensor and the significance for the current status of displacement detection are finally summarized.At the same time,combined with the current research results,the follow-up research direction is prospected,and the optimization direction is proposed.