The correct choice of the optical system is of major importance for the performance of microarray analysis instruments based on fluorescence. A variety of different approaches is possible. The basic concepts are (a) imaging of an extended field on a spatially resolving detector, (b) scanning the microarray with a flat-field lens and (c) scanning by laterally shifting a confocal optical system. Depending on the approach, the optical system may range from a lightweight lens of a few grams to a heavy system with a hundred millimeters in diameter. Further this determines the achievable optical performance in terms of spatial resolution on the microarray and the numerical aperture. Whereas by increasing the numerical aperture more fluorescent photons are captured, a higher spatial resolution avoids cross-talking between spots. But only considering the optics will not render the most efficient concept. The optical system is an integrated part in a number of complex, challenging components. Therefore, the requirements on the optics have often to be balanced with other system specific constraints. A custom-tailored optical design for an instrument under development allows the best compromise and is hereby a fundamental step to achieve maximum overall performance.
"Sophisticated lenses for microarray analysis", Proc. SPIE 4266, Microarrays: Optical Technologies and Informatics, (4 June 2001); doi: 10.1117/12.427975; https://doi.org/10.1117/12.427975