Portable multi-spectral lens-less microscope with wavelength-self-calibrating imaging sensor

Multi-spectral imaging technology is helpful to obtain better contrast and more details of images at different wavelengths compared with monochromatic imaging or conventional RGB imaging technologies. And in resource-limited areas, microscopes with features of low-cost and portability are extremely attractive. In this manuscript, we demonstrate that cost-effective lens-less microscopy can be combined with the multi-spectral imaging technology, which can be alternative to conventional approaches and applied in biology, chemistry, environmental science. As a proof of this concept, we present a novel portable multi-spectral lens-less microscope (MSLLM). An outstanding highlight of our setup is its wavelength-self-calibrating imaging sensor (WSCIS), which can provide computationally optimized wavelength value (COWV) for LED illumination in real time. For each illumination, 5 holograms of the sample at 5 different heights are captured. Through the COWVs and phase retrieval algorithms, 7 multi-spectral images (FOV: 4.8 mm*4.6 mm, resolution: ∼1 µm) can be reconstructed. We believe that our MSLLM can be widely applied to multi-spectral microscopy in low-cost required scenes.