27 research outputs found
Fundamental bounds on the precision of classical phase microscopes
A wide variety of imaging systems have been designed to measure phase
variations, with applications from physics to biology and medicine. In this
work, we theoretically compare the precision of phase estimations achievable
with classical phase microscopy techniques, operated at the shot-noise limit.
We show how the Cram\'er-Rao bound is calculated for any linear optical system,
including phase-contrast microscopy, phase-shifting holography, spatial light
interference microscopy, and local optimization of wavefronts for phase
imaging. Our results show that wavefront shaping is required to design phase
microscopes with optimal phase precision
Optical Near-Field Electron Microscopy
Imaging dynamical processes at interfaces and on the nanoscale is of great
importance throughout science and technology. While light-optical imaging
techniques often cannot provide the necessary spatial resolution,
electron-optical techniques damage the specimen and cause dose-induced
artefacts. Here, Optical Near-field Electron Microscopy (ONEM) is proposed, an
imaging technique that combines non-invasive probing with light, with a high
spatial resolution read-out via electron optics. Close to the specimen, the
optical near-fields are converted into a spatially varying electron flux using
a planar photocathode. The electron flux is imaged using low energy electron
microscopy, enabling label-free nanometric resolution without the need to scan
a probe across the sample. The specimen is never exposed to damaging electrons