All Research Areas

Partioned aperture wavefront imaging

A wavefront imager provides images of the phase and amplitude of a wavefront. Several techniques for wavefront imaging have been developed. Most of these involve the use of a laser, and are thus susceptible to speckle noise. Techniques that do not require a laser generally require collimated light, meaning they are not light efficient, or require moving parts and the acquisition of multiple images, meaning they are slow. We have recently developed a wavefront imager that is fast (single shot), achromatic (works with broadband light), light efficient (works with extended sources), and simple. The technique is based on partitioning the detection aperture of a standard microscope into four quadrants with the use of four off-axis lens. These lenses provide four oblique detection images that are simultaneously acquired with a single camera. The data provided by these four images enables the reconstruction of wavefront phase and amplitude with a simple numerical algorithm that runs in real time (video rate).

Publications Related to this Research Area

View synthesis with a partitioned-aperture microscope

J.-C. Baritaux, C. R. Chan, J. Li, J. Mertz,

Optics Letters

We present a simple and fast algorithm for view synthesis based on the acquisition of four high-resolution oblique images with a conventional widefield microscope. The images are acquired simultaneously using a partitioned aperture add-on. The technique provides physically valid views of thin samples that are transmitting or fluorescent, as demonstrated with biopsied tissue or green fluorescent protein-labeled brain slices. The goal of this technique is to facilitate image interpretation by conferring impressions of depth that are otherwise absent in standard microscope images.

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Single-exposure surface profilometry using partitioned aperture wavefront imaging

R. Barankov, J. Mertz,

Optics Letters

We demonstrate a technique for instantaneous measurements of surface topography based on the combination of a partitioned aperture wavefront imager with a lamp-based reflection microscope using standard objectives. The technique can operate at video rate over large fields of view, and provides nanometer axial resolution and submicrometer lateral resolution. We discuss performance characteristics of this technique, which we experimentally compare with scanning white light interferometry.

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Quantitative phase imaging using a partitioned detection aperture

Ashwin B. Parthasarathy, Kengyeh K. Chu, Tim N. Ford, and Jerome Mertz,

Optics Letters

We present a technique to quantitatively image the phase of thin quasi-transparent samples using extended source incoherent illumination and off-axis detection apertures. Our technique is achromatic and polarization independent, requires no active elements, and can be readily adapted to standard bright-field microscopes. We demonstrate our technique by quantitatively reconstructing the phase of cheek cells and a microlens. The light efficient, single-shot nature of our technique enables phase imaging at frame rates that are camera limited.

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Quatrefoil PAW lens

PAW involves imaging a scene with four offset lenses in the aperture plane. Local light tilts at the scene induce light shifts at the aperture plane (as shown).

Phase image of a cheek cell.

Reconstructed phase image based on phase-gradient images acquired by trans-illumination PAW microscope.

Surface topography of 4 pixels of a deformable mirror

Topography calculated based on phase-gradient images acquired by a PAW microscope in reflection mode. Image acquisition was video rate. Topography precision is about 3nm.