Abstract

The inline holography with pinhole illumination enables a lens-free microscopy up to the diffraction limit, where only slight variations of the refractive index between pinhole and image sensor are permitted. A known technique to take in consideration the influence of glass sample carriers is index matching. In this paper, the lens-free inline holographic microscopy will be extended by the use of microfluidic chips with a total thickness up to 5.5 mm. The image sensor has a distance of about 3 mm to the fluidic chip. That means a long distance imaging with strongly varying refractive indices (air, glass, water-like solutions), which have to be considered. The microfluidic chip is prepared with an integrated pinhole mask and additional reference markers inside the channel. The position of the pinhole, which is needed for reconstruction, will be determined using the also imaged reference markers without the need of separate measurement. So the sample is imaged with spatial resolution corresponding to numerical apertures of more than 0.5. In experiments, erythrozytes and unstained leukocytes are imaged with sub-pixel resolution.

© 2016 Optical Society of America