Lensfree on-chip microscopy over a wide field-of-view using pixel super-resolution

We demonstrate lensfree holographic microscopy on a chip to achieve similar to 0.6 mu m spatial resolution corresponding to a numerical aperture of similar to 0.5 over a large field-of-view of similar to 24 mm(2). By using partially coherent illumination from a large aperture (similar to 50 mu m), we acquire lower resolution lensfree in-line holograms of the objects with unit fringe magnification. For each lensfree hologram, the pixel size at the sensor chip limits the spatial resolution of the reconstructed image. To circumvent this limitation, we implement a sub-pixel shifting based super-resolution algorithm to effectively recover much higher resolution digital holograms of the objects, permitting sub-micron spatial resolution to be achieved across the entire sensor chip active area, which is also equivalent to the imaging field-of-view (24 mm(2)) due to unit magnification. We demonstrate the success of this pixel super-resolution approach by imaging patterned transparent substrates, blood smear samples, as well as Caenoharbditis Elegans. c 2010 Optical Society of America