Abstract
Lensless microscopy requires the simplest possible configuration, as it uses only a light source, the sample and an image sensor. The smallest practical microscope is demonstrated here. In contrast to standard lensless microscopy, the object is located near the lighting source. Raster optical microscopy is applied by using a single-pixel detector and a microdisplay. Maximum resolution relies on reduced LED size and the position of the sample respect the microdisplay. Contrarily to other sort of digital lensless holographic microscopes, light backpropagation is not required to reconstruct the images of the sample. In a mm-high microscope, resolutions down to 800 nm have been demonstrated even when measuring with detectors as large as 138 μm × 138 μm, with field of view given by the display size. Dedicated technology would shorten measuring time.
Highlights
The benefits of lensless microscopy are not questioned, such as low cost, large field of view (FOV) and no need to focus [1,2]
The resolution is limited by the dimension of the detector pixel and the signal-tonoise ratio becomes independent of the field of view (FOV), allowing unique microscopes that can achieve improved both resolution and FOV simultaneously [10]
The performances obtained with the different light sources and operation modes are described
Summary
The benefits of lensless microscopy are not questioned, such as low cost, large field of view (FOV) and no need to focus [1,2]. The technique consists of directly sampling the light transmitted through a specimen located close to a photodetector without the use of any imaging lens. The second configuration puts the sample extremely close to the detector (or aperture), so that diffraction is minimized [9]. Light from an illumination source passes through the specimen and casts a shadow on the sensor with unit magnification. With this setup, the resolution is limited by the dimension of the detector pixel and the signal-tonoise ratio becomes independent of the field of view (FOV), allowing unique microscopes that can achieve improved both resolution and FOV simultaneously [10]. Several strategies have been demonstrated to reduce the effective pixel size at the expense of computational force, such as moving aperture [11] or multi-frame imaging [12]
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