Large field of view MEMS-based confocal laser scanning microscope for fluorescence imaging

Although confocal fluorescence microscopes are widely used in biology and have been proven to be promising diagnostic tools in dermatologic diagnostics, they are at present uncommon in medical practice. This is mainly due to high costs of acquisition and their large and complex outline. With the integration of a MEMS scanner we present a demonstration system of a confocal fluorescence laser scanning microscope which is affordable and portable. It has a field of view of 500 μm × 500 μm and is mainly composed of off-the-shelf components.Since one of the most important factors for obtaining a good, high contrast image is to collect enough photons, it is evident that good optics for optimal collection of light is necessary. These optical performance requirements for the microscope will be discussed in detail. In this design, the MEMS mirror acts as limiting system aperture and directly translates into the amount of laser beam clipping for a given beam diameter. Gaussian beam formulas are valid for an aperture-to-beam-radius T > 1.6. The beam diameter on the other hand translates to necessary relay optics for an addressed Numerical Aperture ≥ 0.4. On the demonstration setup these different figures of merit are discussed and compared with first images taken of biological samples.