Research On Real-time Negative Feedback Axial-focus System Based On PSD

Microscope is an important experimental tool in biology and medical laboratory.The focus drift will make the image resolution of the subsequent records low and the images fuzzy,so that subsequent analyses cannot be carried out.Therefore,it is of great importance to solve the focus drift problem.As a result,a real-time negative feedback axial focusing system based on PSD(Position Sensitive Detector)was set up in this paper.The system mainly includes focus drift detection optical path based on PSD,data acquisition,processing and communication based on DSP(Digital Signal Processing),negative feedback control of piezoelectric stage and upper computer control software.The work done in this article is as follows:1.The focus drift detection optical path based on PSD is designed and built,and the focus drift amplification principle is given.The analysis of the amplification principle provides the reference for the selection of amplification factor.At the same time,the light detector and light source are selected.2.The hardware and software design of the whole system has been completed.The hardware design mainly includes the conversion and amplification of PSD output signal,the input clamp protection of sampling signal,the peripheral circuits for main control and communication part.The software design mainly involves the built-in ADC acquisition,communication firmware and multi-thread control of the host computer.3.The calibration method and process are analyzed,and the circular beam and the slit beam are calibrated respectively.The corresponding calibration curves are obtained.The slit calibration curve has better linearity,which can make the system have higher control precision.4.The control accuracy and response speed of the system are tested on the system,and the test methods are given.The source of the error is analyzed.The control accuracy of the system is 89.51 nm,and the response time is 16 ms,which meet the requirements of microscopic imaging.