University of Twente Student Theses


Investigate an optical readout method for a micro Coriolis mass flow sensor

Wu, Q. (2021) Investigate an optical readout method for a micro Coriolis mass flow sensor.

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Abstract:With the rapid replacement of semiconductor sensor devices, the overall device size continues to shrink. As a sensitive component, the structure usually has micrometer or even nanometer displacement that needs to be accurately measured. The small-displacement detection method with high sensitivity and excellent dynamic response is facing challenges. The purpose of this paper is to design and verify an optical displacement readout system for a micro Coriolis mass flow sensor. The target to be detected is an integrated suspended micro-tube, with millimeter size dimensions and nanometer level out-of-plane displacements. We designed the top surface of the micro-tube as a reflecting mirror and set a fixed grating above it to form a double grating diffraction structure. Based on the theory of grating diffraction, the diffracted order intensity of the composite diffracted light field is sensitive to the displacement of the mirror surface, and the light sensor can be used to convert the detectable light signal into an electrical signal. In this report, the working principle of this double grating diffraction-based readout system is theoretically deduced and a mathematical model is established. Through optical simulation and numerical calculation, it is verified that the detection range of this system meets the requirements of the flow sensor. At the same time, due to the periodicity of the motion pattern of the movable micro-tube, the phase shift analysis method was adopted and high sensitivity (0.03rad per nm) was reached. Based on theoretical research, the related devices selection and layout design of the optical readout system has also been completed. A series of preliminary experiments confirmed that the light signal changes caused by the nano-scale periodic motion can be detected and measured. The thesis initially verified the feasibility of the designed optical reading system, and the actual sensitivity and dynamic performance still require subsequent device fabrication and testing.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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