Sapna A. Shroff

Phase-shift estimation in sinusoidally illuminated images for lateral superresolution

Sinusoidally patterned illumination has been used to obtain lateral superresolution and axial sectioning in images. In both of these techniques multiple images are taken with the object illuminated by a sinusoidal pattern, the phase of the sinusoidal illumination being shifted differently in each image. The knowledge of these phase shifts is critical for image reconstruction. We discuss a method to estimate this phase shift with no prior knowledge of the shifts. In postprocessing we estimate randomly introduced, unknown phase shifts and process the images to obtain a superresolved image. Results of computer simulations are shown.

OTF compensation in structured illumination superresolution images

The lateral resolution of an imaging system is limited by its numerical aperture and the wavelength. Structured illumination incident on the object heterodynes the higher spatial frequencies of the object with the spatial frequency of the sinusoidal illumination into the passband of the imaging system providing lateral superresolution. This idea has been implemented in microscopy. Multiple images of an object are taken, with distinct phase shifts in the sinusoidally patterned illumination. They are processed to separate the conventional, un-aliased object spatial frequencies from the aliased ones, which contain superresolution information. The separated aliased terms are de-aliased (i.e. the spatial frequencies in them are moved to their correct locations in Fourier space) giving superresolution along the direction perpendicular to the orientation of the sinusoidal fringe pattern. This process is repeated with, say, 60° and 120° rotation of the sinusoidal fringe illumination to obtain superresolution in all directions. The final reconstructed image can be obtained by appropriate combination of the de-aliased superresolution components with the conventional, un-aliased components. We discuss the signal-to-noise ratio (SNR) and optical transfer function (OTF) compensation in the combination of all these components to obtain an image with lateral superresolution.

Lateral superresolution using a posteriori phase shift estimation for a moving object: experimental results.

Structured illumination imaging uses multiple images of an object having different phase shifts in the sinusoidally patterned illumination to obtain lateral superresolution in stationary specimens in microscopy. In our recent work we have discussed a method to estimate these phase shifts a posteriori, allowing us to apply this technique to non-stationary objects such as in vivo tissue. Here we show experimental verification of our earlier simulations for phase shift estimation a posteriori. We estimated phase shifts in fluorescence microscopy images for an object having unknown, random translational motion and used them to obtain an artifact-free reconstruction having the expected superresolution.

Estimation of Phase Shifts in Structured Illumination for High Resolution Imaging

The application of structured illumination for enhanced resolution requires accurate knowledge of phase shifts in the sinusoidal illumination. This work proposes a method to estimate random, unknown phase shifts and subsequent image reconstruction.

Phase Shift Estimation in Structured Illumination Imaging for Lateral Resolution Enhancement

Lateral resolution enhancement using structured illumination imaging requires accurate knowledge of phase shifts in the sinusoidal illumination on the object. We discuss a method to estimate these phase shifts and the resulting image reconstructions.

Estimation of Phase Shifts in Structured Illumination for Optically Sectioned Imaging of Moving Objects

Structured illumination has been used to obtain optically sectioned images. We estimate unknown, random phase shifts in the multiple sinusoidally patterned images in post-processing, permitting the application of this technique to translating objects.