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The success of the phase-contrast microscope has led to a number of subsequent phase-imaging methods. In 1952, Georges Nomarski patented what is today known as differential interference contrast (DIC) microscopy. [8] It enhances contrast by creating artificial shadows, as if the object is illuminated from the side.
The route of light through a DIC microscope. The two light beams should be parallel between condenser and objective. 4. The rays travel through adjacent areas of the sample, separated by the shear. The separation is normally similar to the resolution of the microscope.
Like differential interference contrast microscopy (DIC microscopy), contrast is increased by using components in the light path which convert phase gradients in the specimen into differences in light intensity that are rendered in an image that appears three-dimensional. The 3D appearance may be misleading, as a feature which appears to cast a ...
The advantages of these methods compared to normal absorption-contrast X-ray imaging is higher contrast for low-absorbing materials (because phase shift is a different mechanism than absorption) and a contrast-to-noise relationship that increases with spatial frequency (because many phase-contrast techniques detect the first or second ...
The effect of the contrast transfer function can be seen in the alternating light and dark rings (Thon rings), which show the relation between contrast and spatial frequency. The contrast transfer function (CTF) mathematically describes how aberrations in a transmission electron microscope (TEM) modify the image of a sample.
Such objects do, however, induce a phase shift that can be observed using a phase contrast microscope. Conventional phase contrast microscopy and related methods, such as differential interference contrast microscopy, visualize phase shifts by transforming phase shift gradients into intensity variations. These intensity variations are mixed ...
Sample orientation: The sample should first be aligned with the electron beam and tilted to a suitable angle to achieve the desired dark-field contrast. Tilt the sample to a low-index zone axis. Follow the Kikuchi lines to form the two-beam condition that is orienting the sample in bright field mode such that g is excited and s g {\displaystyle ...
As a consequence contrast in the image plane gets its image components from the minimal area of the sample, the contrast is localized (no blurring and information overlap from other parts of the sample). The contrast transfer function becomes a function that oscillates quickly with C s u 4.