Confocal Laser Induced Fluorescence Detection System Based On ARM9

Confocal laser-induced fluorescence detection is one of the main means of Capillary Electrophoresis (CE) chip detection. With its high sensitivity, it can even be used in single molecule detection. However, most of the confocal LIF detection systems are controlled and displayed by computers, which leads to enormous detection system, so miniaturisation and integration is difficult to be implemented. Based on ARM9 processor and embedded Linux operating system, confocal LIF detection system without computer was designed to achieve the functions of chip's image observation, fluorescence signal acquisition and auto focusing.The hardware system of the confocal LIF detection system contains Z-axis electric moving stage control module, optical switching modules, high voltage control module, PMT data acquisition control module and switch module. The software system consists of video image acquisition and processing module, fluorescence acquisition module, high voltage setup module, manual focusing module, switch control module and data storage module. Drivers for the hardware system are running based on embedded Linux operating system, and the software system can control the hardware devices by calling the device driver interface function. Users could operate the detection system by touch screen, and images of chips or detection curves could be shown on the 3.5-inch LCD screen. One small CMOS camera chip OV9650 was used for observation, and the camera driver based on the CAMIF of ARM9 microprocessor was developed to realize the video image acquisition and display, which greatly reduced the size of the detection system. When working on the observation mode, after determining the chip observation location, the system can achieve auto focusing by the images clarity evaluation.Making use of the detection system designed, the states of injection and separation of the sample were observed, which could provide some powerful basis for bio-chip design and determination of the sample separation conditions. The electrophoretic separation experiments were made for different concentrations of Rhodamine B samples in the detection system, and the minimum detection limit of the system is 1×10^-7 mol/L, and the signal-to-noise ratio and repetitiveness of the detection system have reached the design requirements.