Contrast transfer function
Encyclopedia
The contrast transfer function is a type of optical transfer function
that affects images collected in an transmission electron microscope. The contrast transfer function must be corrected in the images in order to obtain high resolution structures in three-dimensional electron microscopy, especially cryo-electron microscopy
.
The oscillations of contrast transfer function has the form (not including the envelope
function):
where r is the radius from the center of the image, Cs is the spherical aberration
, λ is the wavelength of the electron beam (usually converted from the potential difference voltage) and f is the amount of defocus.
Optical transfer function
The optical transfer function of an imaging system is the true measure of resolution that the system is capable of...
that affects images collected in an transmission electron microscope. The contrast transfer function must be corrected in the images in order to obtain high resolution structures in three-dimensional electron microscopy, especially cryo-electron microscopy
Cryo-electron microscopy
Cryo-electron microscopy , or electron cryomicroscopy, is a form of transmission electron microscopy where the sample is studied at cryogenic temperatures...
.
The oscillations of contrast transfer function has the form (not including the envelope
Envelope (mathematics)
In geometry, an envelope of a family of curves in the plane is a curve that is tangent to each member of the family at some point. Classically, a point on the envelope can be thought of as the intersection of two "adjacent" curves, meaning the limit of intersections of nearby curves...
function):
where r is the radius from the center of the image, Cs is the spherical aberration
Spherical aberration
thumb|right|Spherical aberration. A perfect lens focuses all incoming rays to a point on the [[Optical axis|optic axis]]. A real lens with spherical surfaces suffers from spherical aberration: it focuses rays more tightly if they enter it far from the optic axis than if they enter closer to the...
, λ is the wavelength of the electron beam (usually converted from the potential difference voltage) and f is the amount of defocus.