Abstract
We report a lens-free fluorescence imaging device using a composite filter composed of an interference filter and an absorption filter, each applied to one side of a fiber optic plate (FOP). The transmission of angled excitation light through the interference filter is absorbed by the absorption filter. The auto-fluorescence of the absorption filter is reduced by the reflection from the interference filter of normally incident excitation light. As a result, high-performance rejection of excitation light is achieved in a lens-free device. The FOP provides a flat, hard imaging device surface that does not degrade the spatial resolution. We demonstrate excitation rejection of approximately 108:1 at a wavelength of 450 nm in a fabricated lens-free device. The resolution of fluorescence imaging is approximately 12 µm. Time-lapse imaging of cells containing green fluorescent protein was performed in a 5-µm thin-film chamber. The small dimensions of the device allow observation of cell culturing in a CO2 incubator. We also demonstrate that the proposed lens-free filter is compatible with super-resolution bright-field imaging techniques. These features open a way to develop a high-performance, dual-mode, lens-free imaging device that is expected to be a powerful tool for many applications, such as imaging of labeled cells and point-of-care assay.
Highlights
Lens-free imaging is an imaging technique that does not use any lenses [1]
We propose a hybrid filter based on the complementary combination of an interference and absorption filter via an fiber optic plate (FOP)
We demonstrated a hybrid emission filter with an excitation light rejection ratio of 108:1 for a lens-free imaging device
Summary
Lens-free imaging is an imaging technique that does not use any lenses [1]. The lenses in a lens-based wide-area microscope generally lead to a large size and high cost. A lens-free approach makes it feasible to build a wide-area imaging system with small dimensions. Such a system is suitable for observation of a large number of cells and performance of various biomarker assays. Fluorescent labeling is a very important technique for observing biological reactions in cells [12] and microarrays [13, 14]. To overcome this problem, the performance of fluorescence imaging sensitivity needs to improve. The luminescence intensity is typically weak, so the image sensor must have very high sensitivity
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