Hyperspectral fluorescence microscopy requires light sources with a number of excitation wavelength bands from deep UV to visible range to excite native fluorophores of cells and tissues. Achieving adequate optical power and wavelength range in the UV is difficult because the excitation light must be channelled to the sample through the microscope which results in power loss.
We report the design of a light source for fluorescence microscopy which can combine the optical power available from multiple LEDs with the same wavelength range. The light source has the shape of a truncated cone with the exit aperture size of 9 mm which is equivalent to the aperture of a conventional mercury lamp used for fluorescence excitation. We used aluminium reflective coating for all inner surfaces of the cone with 92% reflectivity. We analysed its performance by using a ray tracing software; the efficiency of this light source found to be optimised for the diameter to length ratio of unity, and it was the highest for the smallest size (25mm). Variations of the cone’s efficiency with the positions of LEDs, inter-LED distance, and the angle of LED were determined. The efficiency of the cone depends upon the inner surface area of cone’s lid and slanting sides, and decreases with increasing area. The optimised source has the efficiency of around 28% for 60 mm diameter and length. This efficient design for multi-LEDs illumination is applicable to hyperspectral microscopy and it can be used with any other fluorescence microscopy as a retrofit.
Kashif Islam, Ewa Goldys, Martin Ploschner, and Martin Gosnell, "A Multi-LED light source for Hyperspectral Imaging of cells and tissues (Conference Presentation)," Proc. SPIE 10486, Design and Quality for Biomedical Technologies XI, 104860I (Presented at SPIE BiOS: January 28, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2281230.5751447692001.
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