Spatial light interference microscopy (SLIM)

Abstract

We present spatial light interference microscopy (SLIM) as a new optical microscopy technique, capable of measuring nanoscale structures and dynamics in live cells via interferometry. SLIM combines two classic ideas in light imaging: Zernike’s phase contrast microscopy, which renders high contrast intensity images of transparent specimens, and Gabor’s holography, where the phase information from the object is recorded. Thus, SLIM reveals the intrinsic contrast of cell structures and, in addition, renders quantitative optical path-length maps across the sample. The resulting topographic accuracy is comparable to that of atomic force microscopy, while the acquisition speed is 1,000 times higher. We illustrate the novel insight into cell dynamics via SLIM by experiments on primary cell cultures from the rat brain. SLIM is implemented as an add-on module to an existing phase contrast microscope, which may prove instrumental in impacting the light microscopy field at a large scale.

White-light diffraction tomography of unlabelled live cells

“…At the camera port, the microscope is equipped with a SLIM module, which renders quantitative phase images with subnanometre path-length sensitivity both spatially and temporally (see ref. 16 for details). To measure the axial dimension, the focal plane is scanned through the object by axially translating the objective lens (Fig.…”

“…2a), WDT is label-free and works without sample preparation. Furthermore, the irradiance at the sample plane in WDT is six to seven orders of magnitude lower than in confocal microscopy 16 , which provides a less harmful environment for the sample. Axial data (z-stack) were acquired in steps of 250 nm and a precision of 10 nm was ensured by the piezoelectric nosepiece.…”

“…In recent years, as a result of new advances in light sources, detector arrays and computing power, quantitative phase imaging (QPI), in which optical path-length delays are measured at each point in the field of view, has become a very active field of study 9 . Whether involving holographic or non-holographic methods [10][11][12][13][14][15][16] , QPI presents new opportunities for studying cells and tissues non-invasively, quantitatively and without the need for staining or tagging [17][18][19][20][21][22][23] . Projection tomography using laser QPI has made use of ideas from X-ray imaging and enabled three-dimensional imaging of transparent structures [24][25][26] .…”

Measurement of multispectral scattering properties in mouse brain tissue

“…While a number of QPI approaches for visualizing neurons and brain tissues have been introduced, e.g., digital holographic microscopy [10,11], optical coherence phase microscopy [12], diffraction phase microscopy (DPM) [13,14], spatial light interference microscopy [15,16], they all utilize interferometry as the underlying operating principle. From the interferogram, the alteration in optical pathlength due to tissue is obtained with nanoscale sensitivity.…”

“…This level of sensitivity is difficult to achieve with any other method. However, QPI has been limited to visualizing cultured neurons and very thin histological section (4-5 microns) [10][11][12][13][14][15][16]. The reason is that the light scattering prevents imaging thick tissues.…”