Differences To Normal Optical Microscopes
Unlike a compound light microscope, illumination in a stereo microscope most often uses reflected illumination rather than transmitted (diascopic) illumination, that is, light reflected from the surface of an object rather than light transmitted through an object. Use of reflected light from the object allows examination of specimens that would be too thick or otherwise opaque for compound microscopy. Some stereo microscopes are also capable of transmitted light illumination as well, typically by having a bulb or mirror beneath a transparent stage underneath the object, though unlike a compound microscope, transmitted illumination is not focused through a condenser in most systems. Stereoscopes with specially-equipped illuminators can be used for dark field microscopy, using either reflected or transmitted light.
Great working distance and depth of field here are important qualities for this type of microscope. Both qualities are inversely correlated with resolution: the higher the resolution (i.e. the shorter the distance at which two adjacent points can be distinguished as separate), the smaller the depth of field and working distance. A stereo microscope has a useful magnification up to 100×, comparable to a 10× objective and 10× eyepiece in a normal compound microscope, and is often much lower. This is around one tenth the useful resolution of a normal compound optical microscope.
The large working distance at low magnification is useful in examining large solid objects such as fracture surfaces, especially using fibre-optic illumination. Such samples can also be manipulated easily so as to determine the points of interest. There are severe limitations on sample size in scanning electron microscopy, as well as ease of manipulation in the specimen chamber.
Read more about this topic: Stereo Microscope
Famous quotes containing the words microscopes, optical, differences and/or normal:
““Faith” is a fine invention
When Gentlemen can see—
But Microscopes are prudent
In an Emergency.”
—Emily Dickinson (1830–1886)
“People who have realized that this is a dream imagine that it is easy to wake up, and are angry with those who continue sleeping, not considering that the whole world that environs them does not permit them to wake. Life proceeds as a series of optical illusions, artificial needs and imaginary sensations.”
—Alexander Herzen (1812–1870)
“The mother must teach her son how to respect and follow the rules. She must teach him how to compete successfully with the other boys. And she must teach him how to find a woman to take care of him and finish the job she began of training him how to live in a family. But no matter how good a job a woman does in teaching a boy how to be a man, he knows that she is not the real thing, and so he tends to exaggerate the differences between men and women that she embodies.”
—Frank Pittman (20th century)
“Philosophically, incest asks a fundamental question of our shifting mores: not simply what is normal and what is deviant, but whether such a thing as deviance exists at all in human relationships if they seem satisfactory to those who share them.”
—Elizabeth Janeway (b. 1913)