Laser Interference Microscopy for Nanobiotechnologies

Abstract

Interference microscopy is widely used in different areas of science for comprehensive study of optical and geometric properties of various microand nanoobjects. The fact that phase imaging makes it possible to overcome the classical resolution threshold has been well known since the 1950s (1). However, only recently the progress in electronics and computer technology has allowed the capacities of phase microscopy to be used to the full extent. Presently, many models of interference micro� scopes are available on the market. The specifications of the interference microscopes are consistent with the area of application. Optical profilometers based on whitelight interferometers are most commonly used. Optical pro� filometers are used in semiconductor technology for quality control. In recent years, interference microscopy finds con� tinuously increasing application for studying biological objects. The advantages of interference microscopy are high spatial resolution, noninvasive monitoring, and lack of special requirements for the medium in which the measurement is taking place (vacuum or chemical dyes are not required). Interference microscopy, which is a strong alternative to conventional optic and confocal microscopy, is based on modern methods of interfero� gram processing. These methods include: coherence phase microscopy (2), optical coherence microtomogra� phy (3), coherence correlation interferometry (4), and digital holographic microscopy (5). The main problem of interference microscopy is insufficient correlation between spatial resolution and efficiency. The method of coherence phase microscopy provides lateral resolution up to 100 nm, but a frame 128 × 128 pixels is recorded within 14 sec, which is too long to test the fast processes in biological objects. On the other hand, the method of digital holographic microscopy allows the images to be obtained at a rate 200 frame/sec, but the spatial resolution of the method is below 200 nm, which is inappropriate for visualization of cell organelles or intracellular structures. The goal of this work was to describe a new modifi� cation of modulation interference microscope (MIM) for biomedical research. The MIM detects the distribution of optical and material parameters of the microscopic object of interest (refraction coefficient, reflection coefficient, anisotropy, and polarization) with high spatial and tem� poral resolution.