Laser Induced Fluorescence Detection Device Based On Liquid Lens

Laser induced fluorescence detection(LIFD) technology is one of the most sensitive means to the microfluidic chip detection. However, there are two shortcomings which challenge the development of LIFD seriously. First, the repeatability of detection is not guaranteed due to several unavoidable factors, such as the limited precision of manufacture, wear and tear in operation, and process incongruence. Also, the amount of windows and the detect position is limited which imposes restrictions on the flexibility of microfluidic chip. In this paper, a laser induced fluorescence detection system based on liquid lens and electric displacement platform is designed, which is capable of adjusting focus position in three-dimension automatically according to the information provided by the images.The main work in this thesis is as following:1. A LIFD system based on tunable liquid lens are developed. Instead of using the traditional mechanical axial displacement scanning motion mechanism, the tunable zoom system can implement axial displacement scan by means of the well-designed autofocus feedback current control function. An electric displacement platform is applied to implement the alignment between the laser spot and the channel as well.2. An confocal optical system for LIFD is designed to realize a focal length adjustment in 4.87mm~8.39 mm, which could achieve auto-regulation between laser spot and detection place along optical axis.3. The autofocus and auto-align algorithms for LIFD are accomplished. With the combination of SUSAN operator and the mountain climbing control algorithm, autofocus algorithm can detect microfluidic chip channel in images and focus the optical system on the channel edge by itself. With the help of PCA straight line extraction, the auto-align algorithm can extract the midline of microfluidic chip channel and control the electric platform to complete automatic alignment.4. A tunable liquid lens based LIFD experimental prototype is set up to testify the proposed system and algorithms. Experimental results show that the system can achieve the autofocus of microfluidic chip and the alignment between laser spot and microfluidic chip channel. The work in this thesis provide a possibility to improves the repeatability of LIFD and make it more flexible to design microfluidic chip.