Wide-field,High-resolution Lensless On-chip Microscopy Via Ptychographic Modulation

For conventional microscope platforms,it’s a difficult task to design a high numerical aperture(NA)lens with diffraction-limited performance over a large field of view.As a result,large field of view and high spatial resolution cannot be achieved at the same time.Lensless microscopy,on the other hand,plays an especially prominent role in computational imaging field aimed at achieving high resolution and large field of view.In this paper,ptychographic modulation technology is added in the lensless microscopy platform,and the traditional ptychography is improved.The main innovation is to add a scattering modulation layer to the system to modulate the exit wavefront of the object.A lensless on-chip microscopy via ptychographic modulation is proposed.Thanks to the scattering modulation layer,the cross-correlation algorithm can be used to accurately calculate the positional shift between adjacent diffraction images.A phase recovery algorithm is designed for the lensless microscopy platform to recover the complex object information from a series of original diffraction images.In order to solve resolution limit set by the imager pixel size,another innovation is to add the up-sampling strategy to the phase recovery algorithm to achieve high resolution.Then,on the basis of monochromatic light illumination,multiple wavelengths(488nm,532 nm and 660nm)are added to the imaging platform to illuminate the sample at the same time,and the phase recovery algorithm is improved to recover the corresponding complex information of the sample at different wavelengths.The innovation is to regard the recovered amplitude information as the three channels of the color image,and channels can be merged into a color image.Therefore,color imaging of stained samples by using monochrome image sensor is successfully realized.Finally,a portable and low-cost lensless microscopic imaging platform is designed.A stained esophagus cancer pathological section,an unstained yeast sample and a potato tuber tissue section are used to actually verify the imaging effect.