Design And Fabrication Of An Optical Accelerometer Based On Grating Interference

In modern society, the development of the design and production of accelerometers is so rapid that it makes accelerometers become the main cause of MEMS market. Accelerometers cover the fields of automobile, aero plane and navigation for military. However, accelerometers designed in traditional way can't satisfy the request for good resolution, big dynamic range, highly integration and low cost. In order to improve those characteristics, a novel optical accelerometer based on high-order diffraction beam interference with a built-in PGC (Phase Generated Carrier) modulator was designed and fabricated. A proof-of-concept prototype was tested and achieved a resolution of 96 ng/√Hz with a dynamic range of 60g. By employing optical interference between±1-order diffraction beams from a grating translating perpendicularly to optical beam for acceleration sensing, the accelerometer realized a wide dynamic range while maintaining a high resolution. Compared with prior optical accelerometers, the interference in this structure is free from the affect of short coherence length or beam divergence and whereby a greater than ordinary dynamic range was obtained. The proposed design is also applicable to MOEMS platform, offering a new thought in the design of high performance MOEMS accelerometers.The issue concerned on the research of accelerometers and displacement sensor together with its model and theory design, which mainly contained the following sections:First of all, we concentrated on the understanding and study of the basic concept of accelerometer, including the definition and composition of sensors and definition of accelerometers. The current techniques and principles of acceleration sensing as well as the trends of accelerometers were summarized. Base on the principle of accelerometers, we analyzed both the advantages and disadvantages of various accelerometers.We also described the basic theory of the accelerometer in detail, including the basic mathematical model of the accelerometer, the classification of accelerometers and the main parameters of the accelerometers. All of these provided the theoretical basis of the design of the accelerometer, as well as prototype testing and evaluation.Secondly, the issue developed a complete research on the optical accelerometer, including the principles of diffraction and interference, the sensor theory of inertial force, which was in the format of mass-spring structure, the principle simulation of the structure, and the phase generated carrier modulation and demodulation algorithm. This section was the most important of this project, which aimed to achieve an accelerometer both in high accuracy and large dynamic range.Again, fabrication and assembly of the accelerometer were described in detail, which included the fabrication of sinusoidal amplitude grating, the fabrication of the accelerometer components. The issue introduced CNC precision engraving technology, which has been used for the fabrication process of the accelerometer. The laser spot fusion technology was used for the assembly of the accelerometer. This section illustrates the prototype fabrication and assembly process in laboratory, which was so important that it ensured the performance of accelerometer and was the premise that prototype behavior matched with the theoretical prediction.Finally, when the fabrication and assembly were completed, we carried out the test experiment of the accelerometer. Experimental results show that the proposed optical accelerometers were largely increased in both resolution and dynamic range when compared to conventional accelerometers.