Table 3976. Comparison between optical and electron microscopes.
|
Light/optical microscope |
Electron microscope |
Probe source |
Light source |
Electron source |
Lenses |
A series of simple curved glass lenses |
Electrostatic or electromagnetic lens |
Spatial resolution |
Under optimal conditions (excellent lenses, oil immersion) the resolution is ~ 200 nm. See page4526 |
|
Ability of observing living cells to biologists |
Yes |
No. But stained tissue |
Recording media |
Eye or photographic film |
Phosphor screen or photographic film |
Wavelength of probe |
> 10 nm |
|
Information delivered by the microscope |
Less details |
More details |
|
Shallower due to the properties of its glass lenses (e.g. DoF is ~1 µm) |
Deeper because SEM/STEM don't use lenses to directly form images, but they form images by scanning a focused beam from pixel to pixel, e.g. for a working distance of 20 mm, the DoF is ~0.4 mm at 100x, 40 µm at 1,000x and 4 µm at 10,000x |
Maximum magnification power |
2,000 times |
As high as 20,000,000 times (for TEM); as high as 1,000,000 times (for TEM) |
Operation condition |
Operates at atmospheric pressure |
Operates under high vacuum
to prevent the electron beam from being scattered by gas molecules |
Maintenance |
Easier to maintain |
Not easy |
Typical price |
$100 or more |
More expensive; $100,000 or more |
Main problems |
Low spatial resolution |
Specimens must be fixed in plastic and viewed in a vacuum; specimens can be damaged by the electron beam |
Other differences |
The oldest (Starting in the 17th century), simplest and most widely-used form of microscopy |
Starting in the 20th century |
Specimen limitation |
Any specimens |
Gases cannot be analyzed and liquids are limited to those that have very limited volatility and will not contaminate the column and specimen chamber because specimens must be exposed to vacuum conditions. |