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Dark Field Microscope

Dark field microscope is different from other microscope becausethe image will be seen in a dark background unlike the bright fieldmicroscope. This is because the condenser of the dark field microscope

allows a hollow shape cone of light to pass through the glass slide. Thisunique way of changing the shape of light makes the background black. Ina normal microscope the light will not form a hollow space but it wouldform a filled cone of light that would pass through the slide or the sample.

This is what dark field microscope different with other microscope.

Dark field microscope has a usual low magnification up to 100times. It is usually used to view images in a liquid sample it can also be used to view cells in suspensions.In general dark field microscope is used for:

a. Suspension of cells to smaller specimens such as mitochondrion and chloroplast.b. Protist and metazoan culture in a liquid medium.c. Determines the motility of organisms.

Phase contrast Microscope

Principle involve: Light passing from the illuminator willpass through the condenser. The condenser will in turn focus thelight into the specimen. It will collect the light and prevent it fromscattering. What differentiates phase contrast microscope fromother microscope is that it contains a device that helps the

scattered light after passing through the specimen to be 90degrees shifted. Therefore the scattered light and background light

would be passing in a combined vector called foreground. After theforeground is directed it then passes through the gray filter ring.

Uses: the phase contrast microscope is used to magnify cells. It is used to study how cell divides

and it reveals cell structures that are not normally seen in ordinary microscope.

Differential Interference Contrast (DIC) Microscope

Principle Involve: unpolarized Light passes through the microscope and a then it will bepolarized. The light will then pass through the Nomarski-modified Wollaston prism. The light will beseparated into two rays after passing the prism. The two rays are then are focused in the condenser anddirected to the sample. Now the sample is lighted with 90 degrees polarized light and 0 degreespolarized light. The light will then travel through the objective lens and then to the second Nomarski-modified Wollaston prism. Optical differentiation of the optical path length generates the image seen.

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Uses: The image would appear three dimensionally. It is because of the strong light and darkshadow casted in the images. Therefore DIC microscope is advantageous in sample that needs to beseen with its width. It is also used in unstained but alive biological sample from a cultured tissue or awater borne organism. DIC gives hope for viewing live organism in a three dimensional orientationhowever it is unsuitable for thick samples such as tissue slices and highly pigmented cells. Since

polarization is the mechanism behind this microscope it is unsuitable for non biological samples.

Fluorescence Microscope

Principle: Fluorescence microscope needs aspecific wavelength to work. The wavelength is thenabsorbed by the fluorophores. Fluorophores has theability to sustain the emission of light but it would deter

the color of the light absorbed. A filter would separate thetwo different lights-the illumination light and the

fluorescence light. The fluorescence microscope has adistinct parts of its own. They are the excitation filter anddichroic mirror. The fluorophore gives color to the

specimen. This helps the viewer to distinguish parts of acell.

Use: This microscope could be used by Immunofluorescence. This technique is done for bindingan antibody to its antigen and label the specific proteins or other molecules in the cell. It can also use for

genetics because of fluorescent proteins.

Confocal Micorscope

Principle: Confocal microscope uses point of illumination and a pinhole in the conjugate

plane in front of the detector to eliminate out of focus signal. The sample uses fluorescence so a longerexposure of light is needed for the confocal microscope to be used.

As only one point in the sample is illuminated at a time, 2D or 3D imaging requiresscanning over a regular raster (i.e., a rectangular pattern of parallel scanning lines) in the specimen. Theachievable thickness of the focal plane is defined mostly by the wavelength of the used light divided bythe numerical aperture of the objective lens, but also by the optical properties of the specimen. Thethin optical sectioning possible makes these types of microscopes particularly good at 3D imaging and

surface profiling of samples.

Use: Thin optical sectioning done in the confocal microscope makes the microscopegood at 3 dimensions. There are different kinds of confocal microscope they have differentadvantages from each other but combining their advantages against other microscope onecould say the confocal microscope could control the depth of the specimen and analyze theburied layers in painting.

http://en.wikipedia.org/wiki/Numerical_aperturehttp://en.wikipedia.org/wiki/Objective_lenshttp://en.wikipedia.org/wiki/Optical_sectioninghttp://en.wikipedia.org/wiki/Optical_sectioninghttp://en.wikipedia.org/wiki/Objective_lenshttp://en.wikipedia.org/wiki/Numerical_aperture

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Scanned Probe Microscopy

Principle: Scanning probe microscope uses a physical probe that scans the specimen. Thismicroscope is invented after the scanning tunneling microscope is invented. The principle involve in thismicroscope is its piezoelectric actuators. The actuators has the ability to detect the movement in the

most precise and accurate manner. The actuators are able to apply its ability of motion detection in verysmall size as in molecular and cellular level. Another principle behind this microscope is that the data aretypically obtained as a two-dimensional grid of data points, visualized in false color as a computer image.

Use: Scanning Probe Microscopy provides researchers with a larger variety of specimenobservation environments using the same microscope and specimen reducing the time required toprepare and study specimens.

Specialized probes, improvements and modifications to scanning probe instruments continues toprovide faster, more efficient and revealing specimen images with minor effort and modification.

Scanning Tunneling Microscope

Principle: The principle behind this microscope lies on itscomponents. The scanning tunnelling microscope has sc anning tip,piezoelectric controlled height and x,y scanner, coarse sample-to-tip control, vibration isolation system, and computer. Thismicroscope also has the ability to use the piezoelectric actuators.What lies behind all the components and technique done in theSTM microscope is based on quantum mechanics.

Use: Scanning Tunnelling Microscope had made the pioneer of using the mechanism of quantummechanics by the piezoelectric actuators. They are used for smaller sizes that ordinary microscope isunable to magnify properly. It gives a good dimension of different specimens

Atomic Force Microscope

Principle: STM microscope is unable to magnify specimens incertain conditions which the ATM microscope had overcome. Today mostAFMs use a laser beam deflection system. AFM tips and cantilevers aremicro fabricated from Si or Si3N4. The typical tip radius is from a few to

10s of nm.

The atomic force microscope is one of about two dozen types of

scanned-proximity probe microscopes. All of these microscopes work bymeasuring a local property - such as height, optical absorption, ormagnetism - with a probe or "tip" placed very close to the sample. The

small probe-sample separation (on the order of the instrument's resolution) makes it possible to take

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measurements over a small area. To acquire an image the microscope raster-scans the probe over thesample while measuring the local property in question. The resulting image resembles an image on atelevision screen in that both consist of many rows or lines of information placed one above the other.

Use: AFM today is very widely used for research topics since it gives a very fine image of the

specimens. The AFM also has branched to many application requirements such as contact mode, lateralforce microscop , noncontact mode, dynamic force, force modulation and phase imaging.