A constrained method for lensless coherent imaging of thin samples.

Lensless inline holography can produce high-resolution images over a large field of view (FoV). In a previous work [Appl. Opt.

Compact lensless subpixel resolution large field of view microscope.

We report on a method to increase the spatial resolution in a compact lensless microscope. A compact side illumination is fabricated to illuminate the sample with a collimated beam by diffraction from a volume phase grating. The wavelength of a semi-conductor laser source (vertical-cavity surface-emitting laser) is tuned with the injection current to alter the illumination direction by wavelength selective diffraction from the volume phase grating.

Compact in-line lensfree digital holographic microscope.

Phase imaging provides intensity contrast to visualize transparent samples such as found in biology without any staining. Among them, digital holographic microscopy (DHM) is a well-known quantitative phase method. Lensfree implementations of DHMs offer the added advantage to provide large field of views (several mm compared to several hundred μm) and more compact setups that traditional DHM which have high quality microscope objectives.

Compact lensless off-axis transmission digital holographic microscope.

Current compact lensless holographic microscopes are based on either multiple angle in-line holograms, multiple wavelength illumination or a combination thereof. Complex computational algorithms are necessary to retrieve the phase image which slows down the visualization of the image. Here we propose a simple compact lensless transmission holographic microscope with an off-axis configuration which simplifies considerably the computational processing to visualize the phase images and opens the possibility of real time phase imaging using off the shelf smart phone processors and less than $3 worth of optics and detectors, suitable for broad educational dissemination.

Compact lensless phase imager.

Lensless quantitative phase imaging is of high interest for obtaining a large field of view (FOV), typically the size of the camera chip, to observe biological cell material with high contrast. It has the potential to be widely spread due to its inherent simplicity. However, the tradeoff is the added complexity due to the illumination.