Numerical optical optimization of a micro-LED package for fluorescence microscopy

The principle of fluorescence is used in many areas of microscopy. In biomedicine, it can be used to observe living single cells for cancer research or antibody development. High luminous intensities are required to excite fluorescence, which is why LEDs with visible spectral range are currently used as a light source in conjunction with filters. A critical factor for efficiency of fluorescence microscopy is photobleaching of the fluorophores and phototoxicity, which leads to cell damage. Therefore, this research aims to avoid illumination of cell samples not being examined microscopically. To this end, a micro-LED array is to be developed with which parallel examinations of selected individual samples can be carried out. To enable selective illumination of cell samples a design for the optical package is needed. In addition, the number of examinations that can be carried out simultaneously should be increased. Therefore, the pitch between the samples must be small as possible, which is why the micro-LEDs’ beams must be already influenced in near field. The aim is to achieve homogeneous illumination of the cell sample under investigation with minimal edge scattering and maximal intensity. Using numerical optimization, a design for a freeform micro lens array (MLA) is created. The algorithm adapts to emitted beam shapes resulting from pixel size, pitch, and wavelength, to enable flexible adaptation of the MLA when the system parameters are changed. Finally, the package is simulated and validated using raytracing.