Hoffman modulation contrast microscopy (HMC microscopy) is an
optical microscopy
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviol ...
technique for enhancing the contrast in unstained biological specimens. The technique was invented by Robert Hoffman in 1975. Like
differential interference contrast microscopy
Differential interference contrast (DIC) microscopy, also known as Nomarski interference contrast (NIC) or Nomarski microscopy, is an optical microscopy technique used to enhance the contrast in unstained, transparent samples. DIC works on the ...
(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 shadow may not necessarily have a distinct physical geometry corresponding to the shadow. The technique is particularly suitable for optical sectioning at lower magnifications.
[Douglas B. Murphy (2001): ''Fundamentals of light microscopy and electronic imaging'', Wiley-Liss, Inc., New York, ][http://www.olympusmicro.com/primer/techniques/hoffman.html]
An example of the use of HMC illumination is in
in-vitro fertilisation
In vitro fertilisation (IVF) is a process of fertilisation where an egg is combined with sperm in vitro ("in glass"). The process involves monitoring and stimulating an individual's ovulatory process, removing an ovum or ova (egg or eggs) f ...
, where under brightfield illumination the near-transparent oocyte is hard to see clearly.
HMC systems typically consist of a
condenser with a slit aperture, an
objective
Objective may refer to:
* Objective (optics), an element in a camera or microscope
* ''The Objective'', a 2008 science fiction horror film
* Objective pronoun, a personal pronoun that is used as a grammatical object
* Objective Productions, a Brit ...
with a slit aperture, and a
polariser
A polarizer or polariser is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. It can filter a beam of light of undefined or mixed polarization into a beam of well- ...
which is fitted between the condenser and the illumination source and is used to control the degree of contrast. The principle of HMC is used by a number of microscope manufacturers who have introduced their own variants of the technique.
References
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Microscopy