From Wikipedia, the free encyclopedia
A
microscope (from the
Greek:
μικρός,
mikrós, "small" and
σκοπεῖν,
skopeîn,
"to look" or "see") is an
instrument to see objects too
small for the naked eye. The science of investigating small objects
using such an instrument is called
microscopy.
Microscopic means
invisible to the eye unless aided by a microscope.
History
The first detailed account of the interior construction of
living tissue based on the use of a microscope did not appear until
1644, in Giambattista Odierna's
L'ochio della mosca, or
The Fly's Eye.
[3]It was not until the 1660s and 1670s that the microscope was
used seriously in Italy, Holland and England. Marcelo Malpighi in
Italy began the analysis of biological structures beginning with
the lungs.
Robert
Hooke's
Micrographia had a huge impact,
largely because of its impressive illustrations. The greatest
contribution came from
Antoni van
Leeuwenhoek who discovered red blood cells and spermatozoa. On
9 October 1676, Leeuwenhoek reported the discovery of
micro-organisms.
[4]The most common type of microscope—and the first invented—is the
optical
microscope. This is an
optical instrument containing one or more
lenses producing
an enlarged image of an object placed in the focal plane of the
lenses.
Types
Optical
microscopes,
using visible wavelengths of light, are the
simplest and most used. Optical microscopes have
refractive glass and
occasionally of plastic or
quartz, to focus light into the eye or another
light detector. Mirror-based optical microscopes operate in the
same manner. Typical magnification of a light microscope, assuming
visible range light, is up to 1500x with a
theoretical
resolution limit of around 0.2
micrometres or 200
nanometers. Specialized techniques (e.g.,
scanning confocal
microscopy,
Vertico
SMI) may exceed this magnification but the resolution is
diffraction limited.
The use of shorter wavelengths of light, such as the ultraviolet,
is one way to improve the spatial resolution of the optical
microscope, as are devices such as the
near-field scanning
optical microscope.
Sarfus, a recent optical
technique increases the sensitivity of standard optical microscope
to a point it becomes possible to directly visualize nanometric
films (down to 0.3 nanometer) and isolated nano-objects (down to
2 nm-diameter). The technique is based on the use of
non-reflecting substrates for cross-polarized reflected light
microscopy.
Ultraviolet light
enables the resolution of microscopic features, as well as to image
samples that are transparent to the eye.
Near infrared light
images circuitry embedded in bonded silicon devices, as silicon is
transparent in this region. Many wavelengths of light, ranging from
the ultraviolet to the visible are used to excite
fluorescence emission
from objects for viewing by eye or with sensitive cameras.
The traditional optical microscope has been recently modified
into a
digital microscope, where instead of
directly viewing the object, a charge-coupled device (CCD) camera
projects the image to a monitor.
Electron
microscopes
Three major variants of electron microscopes exist:
Established
types of scanning probe microscopy
- AFM, atomic force
microscopy
- BEEM, ballistic electron
emission microscopy
- EFM, electrostatic force
microscope
- ESTM electrochemical
scanning tunneling microscope
- FMM, force modulation microscopy
- KPFM, kelvin probe force
microscopy
- MFM, magnetic
force microscopy
- MRFM, magnetic resonance
force microscopy
- NSOM, near-field scanning optical microscopy (or
SNOM, scanning near-field optical microscopy)
- PFM, Piezo Force Microscopy
- PSTM, photon scanning tunneling microscopy
- PTMS, photothermal
microspectroscopy/microscopy
- SAP, scanning atom probe [5]
- SECM, scanning electrochemical microscopy
- SCM, scanning capacitance
microscopy
- SGM, scanning gate microscopy
- SICM, scanning
ion-conductance microscopy
- SPSM spin polarized
scanning tunneling microscopy
- SThM, scanning thermal
microscopy[1]
- STM, scanning
tunneling microscopy
- SVM, scanning voltage
microscopy
- SHPM, scanning
Hall probe microscopy
- SSM, Scanning SQUID
microscope
Of these techniques AFM and STM are the most commonly used
followed by MFM and SNOM/NSOM.
Other
microscopes
Scanning acoustic
microscopes use sound waves to measure variations in acoustic
impedance. Similar to
Sonar in
principle, they are used for such jobs as detecting defects in the
subsurfaces of materials including those found in integrated
circuits.
See also
References
- ^
Microscopes: Time
Line
- ^
Stephen Jay Gould(2000). The Lying Stones of Marrakech, ch.2 "The
Sharp-Eyed Lynx, Outfoxed by ature". London: Jonathon Cape. ISBN
0224050443
- ^
Bad Medicine: Doctors doing harm since Hippocrates. David Wootton.
Oxford University Press, 2006.
- ^ see Wootton, David
(2006) p. 119.
- ^
Morita, Seizo. Roadmap of Scanning Probe Microscopy. 3 January
2007
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