Study On Confocal Laser Induced Fluorescence Detecting Device

Laser induced fluorescence (LIF) detection is one of the main means of Capillary Electrophoresis (CE) chip detection, in which confocal detecting device is the most commonly used means of detection for the higher sensitivity and signal-to-noise ratio (SNR). The focus operation is very diffcult for the imaging characteristic of confocal system. At present it mostly depends on manual operation, whose reliability and repeatability is poor. This paper designs a LIF detection device that can auto focus based on image processing after analyzing the related study at home and abroad.Based on confocal LIF detection principle, this paper designs a CCD aided measuring and optical switching device. After acquiring defocusing status and position of moving target by image processing, electric moving stages are driven to execute auto focusing and auto tracking. Lower computer control system based on AT89C52 microcontroller is designed and programe is written in Keil C language. The system achieves many functions, such as 3-dimensional electric moving stage control, optical switching, high voltage control, signal acquisition, security protection, etc.. It can run in off-line mode or on-line mode. Users can use keyboard and LCD to operate the device in off-line mode. It can communicate with upper computer through serial port in on-line mode.Upper computer programme is written in VC++. The functions it achieces are as follows: acquiring CCD image using image card, accomplishing image preprocessing such as noise reduction and gridding, performing routine operation such as image saving and opening. Z axis electric moving stage is driven to make CE chip focused based on the definition function value. Coarse adjustment and fine adjustment is both adopted to speed up focusing process. X axis and Y axis electric moving stages are driven to track object based on its position which is calculated by improved 3 frame difference algorithm. Fluorescence data is received and displayed as a real-time curve.The device this paper designs and builds can accomplish the task of auto focusing, auto tracking and fluorescence signal acquisition. It can watch, test and acquire data in every phase of the study of CE chip, which offers the foundation of farther study. This device basically yields the expected results for its automatization and easy using characteristic.