Aberrations - Revision history

Bpappas at 19:21, 4 May 2010

2010-05-04T19:21:20Z

Bpappas at 19:19, 4 May 2010

2010-05-04T19:19:01Z

Bpappas: /* Spherical Aberration */

2010-05-04T19:16:41Z

‎Spherical Aberration

Bpappas at 15:47, 4 May 2010

2010-05-04T15:47:54Z

Bpappas at 15:46, 4 May 2010

2010-05-04T15:46:38Z

Bpappas at 22:24, 30 April 2010

2010-04-30T22:24:04Z

Bpappas at 22:23, 30 April 2010

2010-04-30T22:23:32Z

Bpappas: Created page with ' However, in the EM, electromagnetic lens aberrations, particularly from the objective lens, ultimately limit the resolution of the microscope. ==Spherical Aberration== ==Chro…'

2010-04-30T21:30:35Z

Created page with ' However, in the EM, electromagnetic lens aberrations, particularly from the objective lens, ultimately limit the resolution of the microscope. ==Spherical Aberration== ==Chro…'

New page

However, in the EM, electromagnetic lens aberrations, particularly from the objective lens, ultimately limit the resolution of the microscope.

==Spherical Aberration==

==Chromatic Aberration==

==Axial Astigmatism==

==Coma Aberration==

==Effects on the Resolution limit of the TEM==

@@ Line 13: / Line 13: @@
 The electromagnetic lenses in the EM have a stronger magnetic field toward the outside of the lens. This means that the further off axis an electron is traveling, the more strongly it is bent back to the axis. This causes what begins as a point in the object to become a disc in the image.
-[[File:Example.jpg]]
+[[File:NoCs.jpg|500px]]
+[[File:Cs.jpg|500px]]
-[[File:NoCs.jpg]]
+[[File:CsExp.jpg|500px]]
 ==Chromatic Aberration==

← Older revision		Revision as of 19:19, 4 May 2010
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	The electromagnetic lenses in the EM have a stronger magnetic field toward the outside of the lens. This means that the further off axis an electron is traveling, the more strongly it is bent back to the axis. This causes what begins as a point in the object to become a disc in the image.		The electromagnetic lenses in the EM have a stronger magnetic field toward the outside of the lens. This means that the further off axis an electron is traveling, the more strongly it is bent back to the axis. This causes what begins as a point in the object to become a disc in the image.
		+
		+	[[File:Example.jpg]]

	[[File:NoCs.jpg]]		[[File:NoCs.jpg]]

← Older revision		Revision as of 19:16, 4 May 2010
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	==Spherical Aberration==		==Spherical Aberration==
		+
		+	The electromagnetic lenses in the EM have a stronger magnetic field toward the outside of the lens. This means that the further off axis an electron is traveling, the more strongly it is bent back to the axis. This causes what begins as a point in the object to become a disc in the image.
		+
		+	[[File:NoCs.jpg]]
		+
		+	[[File:Cs.jpg]]
		+
		+	[[File:CsExp.jpg]]

	==Chromatic Aberration==		==Chromatic Aberration==

@@ Line 2: / Line 2: @@
 [[File:Bragg.jpg]]
 Where ''n'' is the refractive index of the vacuum (which is equal to 1); ''sinθ'' is equal to 1, since the numerical aperture for an electron microscope is very narrow.
 However, electromagnetic lens aberrations, particularly from the objective lens, ultimately limit the resolution of the microscope. The typical resolution limit reported for TEM is only about 1 angstrom (about 100 times worse than the theoretical limit).

@@ Line 1: / Line 1: @@
-Considering merely the de Broglie wavelength of electrons accelerated at 100kV (a common accelerating voltage for biological-EM), the electron microscope performs dismally compared to how it theoretically could. The wavelength for such and electron is 0.037 angstroms. The theoretical minimum separation that could be resolved with this wavelength is thus:
+Considering merely the de Broglie wavelength of electrons accelerated at 100kV (a common accelerating voltage for biological-EM), the electron microscope performs dismally compared to how it theoretically could. The wavelength for such and electron is 0.037Å. The theoretical minimum separation, ''d'', that could be resolved with this wavelength is thus (from Bragg's law):
-d=&lambda\over\2n\sin &theta
+[[File:Bragg.jpg]]
-d=.037\over\2 &times 1 &times 1
+Where ''n'' is the refractive index of the vacuum (which is equal to 1); ''sinθ'' is equal to 1, since the numerical aperture for an electron microscope is very narrow.
 However, electromagnetic lens aberrations, particularly from the objective lens, ultimately limit the resolution of the microscope. The typical resolution limit reported for TEM is only about 1 angstrom (about 100 times worse than the theoretical limit).

@@ Line 1: / Line 1: @@
 Considering merely the de Broglie wavelength of electrons accelerated at 100kV (a common accelerating voltage for biological-EM), the electron microscope performs dismally compared to how it theoretically could. The wavelength for such and electron is 0.037 angstroms. The theoretical minimum separation that could be resolved with this wavelength is thus:
-<math>x</math>
+d=&lambda\over\2n\sin &theta
-d{{=}}&lambda\over\2n\sin &theta
+d=.037\over\2 &times 1 &times 1
-d{{=}}.037\over\2 &times 1 &times 1
+d=0.0185 Å
 Where n is the refractive index of the vacuum (which is equal to 1).sin &theta is equal to 1 as well, since the numerical aperture for an electron microscope is so narrow.

← Older revision		Revision as of 22:23, 30 April 2010
Line 1:		Line 1:
		+	Considering merely the de Broglie wavelength of electrons accelerated at 100kV (a common accelerating voltage for biological-EM), the electron microscope performs dismally compared to how it theoretically could. The wavelength for such and electron is 0.037 angstroms. The theoretical minimum separation that could be resolved with this wavelength is thus:

		+	<math>x</math>

−	~~However~~, in the EM, electromagnetic lens aberrations, particularly from the objective lens, ultimately limit the resolution of the microscope.	+	d{{=}}&lambda\over\2n\sin &theta
		+
		+	d{{=}}.037\over\2 &times 1 &times 1
		+
		+	d{{=}}0.0185 Å
		+
		+	Where n is the refractive index of the vacuum (which is equal to 1).sin &theta is equal to 1 as well, since the numerical aperture for an electron microscope is so narrow.
		+
		+	However, electromagnetic lens aberrations, particularly from the objective lens, ultimately limit the resolution of the microscope. The typical resolution limit reported for TEM is only about 1 angstrom (about 100 times worse than the theoretical limit).

	==Spherical Aberration==		==Spherical Aberration==