Study On Real Time Image Detection Technology For The Location Of Microsphere In Dual Beam Optical Trap

Dual-beam optical traps can be used to manipulate mesoscopic particles in many ways,such as translation,rotation,stretching,traction and combination,and it has the features of non-contact and non-injury.It provides researchers with a simple,efficient and widely applicable powerful means to carry out the research in many fields such as biocytology and basic physics at mesoscopic scale,which leads to many new research directions.One of the key technologies of the ultra-sensitive acceleration sensing is the precise measurement of the displacement of the captured microsphere.Currently image detection has been one of the most common methods in the measurement of displacement.The method is simple and easy to reach spatial resolution of nm scale and temporal resolution of kHz.Thus position detections using image analysis in real time are needed in acceleration sensing.Based on this background,the real-time measurement technology of microsphere displacement in dual-beam optical trap is studied in this paper.The main research includes the following two aspects.1.Precise calibration of image coordinate system in double beam optical trap.The concept of the misalignment of the image coordinate system is proposed.In the case of small angle misalignment,the Brownian motion of two-dimensional restricted microsphere is simulated by Monte-Carlo method.The weak position fluctuation caused by Brownian motion proves that even in the case of small angle and weak displacement,misalignment will still bring great error to the calibration of the stiffness of the optical trap.In order to reduce the error,the misaligned angle should be measured in order to compensate the position observations.Two methods based on multi-position observations are proposed:power imbalance method and optical binding method,and the advantages and disadvantages of the two methods are compared.The power imbalance method is chosen due to the actual demand of the acceleration sensing.The single beam emission of a single microsphere is observed in a dual-beam optical trap experiment system,and the misalignment angle is calculated,which have validated the power imbalance method.2.Real-time position detections in dual-beam optical traps.The experimental system is built and a real-time measurement software is configuring using LabVIEW.After pre-treatments,the parameters of the camera are optimized.The displacement resolution has been reached to 10nm/Hz^1/2,which has satisfied the need in current engineering.