Editing Microscopy (section)

==== Phase contrast ====
[[File:Hypertrophic Zone of Epiphyseal Plate.jpg|thumb|250px| Phase-contrast [[light micrograph]] of undecalcified [[hyaline cartilage]] showing [[chondrocyte]]s and [[organelle]]s, [[Lacuna (histology)|lacunae]] and [[extracellular matrix]]]]
{{Main|Phase contrast microscopy}}
: ''In [[electron microscopy]]: [[Phase-contrast imaging]]''
More sophisticated techniques will show proportional differences in optical density. '''Phase contrast''' is a widely used technique that shows differences in [[refractive index]] as difference in contrast. It was developed by the Dutch physicist [[Frits Zernike]] in the 1930s (for which he was awarded the Nobel Prize in 1953). The nucleus in a cell for example will show up darkly against the surrounding cytoplasm. Contrast is excellent; however it is not for use with thick objects. Frequently, a halo is formed even around small objects, which obscures detail. The system consists of a circular annulus in the condenser, which produces a cone of light. This cone is superimposed on a similar sized ring within the phase-objective. Every objective has a different size ring, so for every objective another condenser setting has to be chosen. The ring in the objective has special optical properties: it, first of all, reduces the direct light in intensity, but more importantly, it creates an artificial phase difference of about a quarter wavelength. As the physical properties of this direct light have changed, interference with the diffracted light occurs, resulting in the phase contrast image. One disadvantage of phase-contrast microscopy is halo formation (halo-light ring).