Reflection interference contrast microscopy of arbitrary convex surfaces

Abstract

Current accurate applications of reflection interference contrast microscopy (RICM) are limited to known geometries; when the geometry of the object is unknown, an approximated fringe spacing analysis is usually performed. To complete an accurate RICM analysis in more general situations, we review and improve the formulation for intensity calculation based on nonplanar interface image formation theory and develop a method for its practical implementation in wedges and convex surfaces. In addition, a suitable RICM model for an arbitrary convex surface, with or without a uniform layer such as a membrane or ultrathin coating, is presented. Experimental work with polymer vesicles shows that the coupling of the improved RICM image formation theory, the calculation method, and the surface model allow an accurate reconstruction of the convex bottom shape of an object close to the substrate by fitting its experimental intensity pattern.

A nanometre-scale resolution interference-based probe of interfacial phenomena between microscopic objects and surfaces

“…For comparison, two of these contours are obtained by means of discrete non-planar (using arbitrary small increments, see Supplementary Methods) and planar (traditional analysis910) methods, and a third one is computed after solving the ODE in equation (5). The accuracy of these near-instantaneous procedures is then verified by comparing their predictions with the most accurate analysis available, using the full non-planar model of RICM16 requiring ~1 h of computation time (non-planar fit in Fig. 6a–c).…”

“…3). Instead of applying the complete non-planar interface image formation theory, where all possible contributions to the observed intensity must be individually determined16, we consider a simplified two-dimensional model whereby a single set of complementary rays, I 0 , interfere to produce the intensity observed at a position x in the interferogram, I ( x ). For the single-layer system in Fig.…”

“…4b. Therefore, equation (4) enables direct measurement of inclination angles of wedge-shaped interfaces (from 0° to β * ), such as small contact angles of liquid droplets, avoiding the use of fittings or angular correction factors based on full non-planar theory calculations151633.…”

“…Interference of light reflected back from different optical interfaces in the system directly reveals the existence of contact phenomena, if any, while the characteristic fringe pattern that emerges inherently embeds detailed information about the object’s shape near the substrate at up to a microsecond-scale temporal resolution8. Reflection interference contrast microscopy (RICM)91011 employs non-planar interface image formation theory as a basis to extract this information and accurately reconstruct the surface profile, but its mathematical complexity renders the model cumbersome to implement in its full form1213141516. These difficulties have stimulated development and continuous use of approaches that simplify the connection between the object’s shape and the spacing between neighbouring fringes in the interferogram101718192021.…”

Radial profile detection of multiple spherical particles in contact with interacting surfaces

“…With such a model as a foundation and with knowledge of the relevant parameters, it is possible to accurately simulate RICM profiles. Using non-planar image formation theory and numerical profile reconstruction, Contreras-Naranjo et al [8, 9] developed more advanced algorithms showing improved profile reconstruction of unknown convex particle shapes. Clack and Groves [10] utilized the model of Wiegand et al to create a library of 1250 synthetic templates for automated analysis of RICM images.…”