Design and implementation of lens for fast biochip detection system

Abstract

Raising the scanning speed of a detection system is indispensable for practical applications of biochips such as fast clinical diagnoses and high-throughput filtration. Compared with PMT-based confocal scanning system, CCD-based one can afford simultaneous illumination and detection of multiple pixels with high speed. The performance of imaging lens system plays an important role in CCD-based fluorescence collection and imaging systems. The sensitivity, speed and resolution of the detection system are controlled by numerical aperture, field and aberration of lens system respectively. One of the key technologies of fast biochip detection system refers to the design of the imaging lens system. In this paper, the main characteristics of CCD-based fluorescence collection and imaging system are analyzed in detail, and an imaging lens system is designed to meet the requirements of fast scanning. An optical design software ZEMAX is applied to design and optimize the imaging lens system. The system parameters such as modulation transfer function and field curvature and distortion are obtained. The imaging of standard biochip samples with cyanine (CY5) dye dots on glass substrates are realized by our manufactured lens system. Results show that our lens system is suitable for biochip scanning system with high speed and high sensitivity. Its system parameters are as: numerical aperture for 0.52, viewing field for 10 mm, working distance for 22.5 mm, spatial resolution for 10um and small aberrations. The limitations of the imaging lens system and the routes for further improvement are discussed.