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Types of Microscopes Compared
- Slide microscope
- Stereo microscope
- Digital microscope
- 3D Digital microscope
- USB microscope
- Transmission electron microscope
- Scanning electron microscope
- Scanning probe microscope
Additional reading on microscopes:
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1) Slide microscope
- Magnification: Uses lenses arranged in series, made of optical material that bends light. All magnification takes place via lenses. Uses diascopic illumination (that is, light is transmitted through the specimen). Magnification up to about 1000x.
- Depth of field: Small.
- Uses: Pathology, microbiology, forensics, education
- Advantages: Color viewing. Require no electricity except for the light source. Can be used on living samples. Simple models are relatively common and inexpensive.
- Disadvantages: Usually requires prepared slides and cannot examine objects well in three dimensions.
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2) Stereo microscope, also known as a dissecting microscope
- Magnification: As in a slide microscope, but arranged in two optical paths at slightly different angles to allow the user to view objects in three dimensions. Uses episcopic illumination (light is reflected from the specimen's surface). Maximum useful magnification is about 100x.
- Depth of field: Large.
- Uses: Microsurgery, fine repair, dissection, paleontology, quality control, sorting, forensics.
- Advantages: Color viewing. Can be used on living samples. Requires little or no preparation of the sample.
- Disadvantages: Low magnification.
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3) Digital microscope
- Magnification: Uses both optical lenses and CCD or CMOS sensors; up to at least 1000x magnification.
- Depth of field: Like a regular slide microscope.
- Uses: All the uses of slide microscopes. Especially useful for applications requiring digital information exchange such as telepathology and continuing medical education.
- Advantages: All the advantages of slide microscopes, plus the ability to create "virtual slides" and digital information sharing.
- Disadvantages: Requires a power source to operate. Most also require a computer, although some include their own viewscreens.
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4) 3D digital microscope
- Magnification: Works like a regular digital microscope to achieve up to 1000x magnification.
- Depth of field: Large, up to 20 times greater than that of a slide microscope.
- Uses: All the uses of other digital microscopes, as well as parts machining, materials science, and additional applications.
- Advantages: Object can be viewed from almost any angle and its three-dimensional features can be examined.
- Disadvantages: As with regular digital microscopes. Can be expensive.
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5) USB microscope
- Magnification: Up to 200x.
- Depth of field: Relatively small.
- Uses: Document examination, detail work, hobbies, education, entertainment
Advantages: Can be used on almost any object and requires no preparation of the specimen. Inexpensive. Can usually be purchased for under $130 USD.
- Disadvantages: Not well suited to the same scientific applications as other optical microscopes.
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6) Transmission electron microscope
- Magnification: A series of electrostatic and electromagnetic lenses act on an electron beam to produce up to 50 million times magnification
- Depth of field: Very small.
- Uses: Microbiology, pathology, crystallography
- Advantages: Very high resolution.
- Disadvantages: Requires extensive specimen preparation, including staining and sectioning with an ultramicrotome. Cannot observe the surface of objects.Very specialized equipment that requires a partial vacuum.
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7) Scanning electron microscope
- Magnification: Electrostatic and electromagnetic lenses, as with a TEM. Magnification ranges from 25x to 250,000x.
- Depth of field: Large compared to that of a transmission electron microscope.
- Uses: Biology, microbiology, geology, nanotechnology, crystallography
- Advantages: Can view objects' three-dimensional surface. Also, an SEM can provide information about the specimen's elemental composition.
- Disadvantages: As with TEM, requires specialized equipment and a partial vacuum. Cannot be used on living specimens.
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8) Scanning probe microscope
- Magnification: Uses no lenses at all. Instead, the image is formed by making physical contact with a specimen with a probe, which moves across the specimen in a raster pattern. Scanning probe microscopes can detect features as small as a few picometers in width. (A picometer is a trillionth of a meter, or a thousandth of a nanometer.)
- Depth of field: Varies according to technique.
- Uses: Nanotechnology, biology, microbiology, molecular biology, pathology, food research
- Advantages: Unparalleled resolution. The physical interaction between the probe and specimen can be used to change the specimen, for example by etching it, in a process called nanolithography.
- Disadvantages: Image acquisition is slow and the image size is small. Solid-solid and liquid-liquid interfaces provide a challenge.