Generation of multiple sheets of light using spatial-filtering technique

Curtailed light sheet microscopy for rapid imaging of macroscopic biological specimens

We study the feasibility of volume imaging from a few angular views/scans in a light sheet fluorescence microscopy. Two-dimensional (2D) images (angular views) were acquired at an angular separation of 10° and volume images were constructed with merely 18, 9, and 6 views. We study the structural changes in a 5-day old Zebrafish embryo labeled with Phalloidin TRITC that binds to F-Actin of embryo cell. To collect the data, the specimen is rotated (for varying sampling angles Δθ) with respect to a fixed vertical axis passing through the volume-of-interest (yolk sac). In the proposed realization of selective plane illumination microscopy (SPIM) technique, the translation is completely avoided. Analysis shows rich structural information with marginal reduction in contrast. Comparison with the state-of-the-art SPIM shows appreciable volume reconstruction (from an order less 2D scans) that may be good enough for rapid monitoring of macroscopic specimens. Microsc. Res. Tech. 79:455-458, 2016. © 2016 Wiley Periodicals, Inc.

Toward the optical "magic carpet": reducing the divergence of a light sheet below the diffraction limit

In 3D, diffraction-free or Bessel beams are well known and have found applications in diverse fields. An analog in 2D, or pseudonondiffracting (PND) beams, is a nontrivial problem, and existing methods suffer from deficiencies. For example, Airy beams are not highly localized, some PND beams have significant side lobes, and a cosine beam has to be truncated by a very narrow aperture thus discarding most of the energy. We show, both theoretically and experimentally, that it is possible to generate a quasi-nondiffracting 2D light beam in a simple and efficient fashion. This is achieved by placing a mask consisting of a pair of double slits on a cylindrical lens. The applications include light sheet microscopy/optical sectioning and particle manipulation.

Temporal resolution in fluorescence imaging

Temporal resolution is a key factor for imaging rapidly occurring events in biology. In this feature article, I investigate an approximate estimate for determining the temporal resolution limit. The condition that led to this limit is, the time taken by the ensemble (99.9%) of excited molecules to relax to ground state, assuming all the emitted photons are detected. In a simplistic three-level system, the temporal resolution is, ≈3τ p , where τ p = (log e 10)/(kf + knr ) and, kf and knr are respectively the radiative and non-radiative emission rates. This further assumes the ideal condition that, the quantum efficiency of the detector is unity and there are no other loses. We discuss few state-of-art microscopy techniques that are capable of high temporal resolution. This includes techniques such as multifocal multiphoton microscopy (MMM), multifocal plane microscopy, multiple excitation spot optical microscopy (MESO), multiplane microscopy and multiple light-sheet microscopy (MLSM).