Spiral Phase Contrast Microscopy

Fluorescence microscopy, for instance, has become an indispensable tool in biomedical research. The basic idea behind phase contrast (PC) methods is to convert phase variations into intensity modulations by means of optical manipulations, allowing one to image native, unstained samples with good contrast. The generic arrangement for Fourier filtering is shown in this chapter. Optical vortices have a helical phase profile and thus carry orbital angular momentum. They have been investigated in various contexts. In optical micromanipulation, phase holograms with a helical phase profile are used to create Laguerre-Gauss beams, which carry orbital angular momentum and can trap dielectric particles depending on the relative refractive index, either in the center or in the intensity ring. Spiral phase contrast (SPC) can be emulated on an spatial light modulators (SLMs) screen, but it is also possible to upgrade a microscope for spiral phase imaging with a spiral phase plate. Controlled Vocabulary Terms microscopy; optical vortices; spatial light modulators