The Data Acquisition/Processing/Control System Based On FPGA

Optical tweezers is based on the balance of the scattering force and the gradient force to stably trap the medium particles near the focus of light.When the trapped particle deviates from the center of the trap,the particle will receive an optical trapping force pointed to the center of the trap.By measuring optical trapping stiffness,the force exerted on the particle by optical tweezers can be obtained,mechanical properties of optical tweezers is understood.In order to satisfy the requirement of the optical trap stiffness measurement experiment,a data acquisition/processing/control system is designed and developed,which uses a four-quadrant detector to track the particle's displacement,FPGA as a main controller and USB2.0 interface to connect with the PC.The theories and methods of the data acquisition,data storage,data processing,motor controlling and signal generator are introduced.The hardware contains signal conditioning circuit,A/D converter circuit,D/A converter circuit,USB2.0 interface circuit,FPGA circuit and power circuit.The software contains USB firmware,USB driver and PC application program.Experiment shows that in the system,the displacement of the trapped particle can be collected,stored and processed,and the on-line optical trap stiffness measurement can be performed.Through motor system,zero alignment of the four-quadrant detector is realized.And the system could generate analog signals whose waveform,frequency,amplitude,phase and the number of cycles are adjustable.