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The substage condenser gathers light from the microscope light source and concentrates it into a cone of light that illuminates the specimen with uniform intensity end the entire viewfield. It is an important that the condenser irradiate cone be properly changed to optimize the intensity and angle of irradiate entering the target front lens. Each time an objective is changed, a equivalent adjustment have to be performed on the substage condenser to administer the ideal light cone because that the numerical aperture that the brand-new objective.

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As a an outcome of no optical correction, the Abbe condenser is suited greatly for routine observation with goals of modest number aperture and magnification. The primary advantages of the Abbe condenser are the wide cone of illumination that the condenser is qualified of producing and also its capacity to work-related with long working street objectives. Many microscopes are provided by the manufacturer through an Abbe condenser together the default and these condensers are actual workhorses for regimen laboratory use.

The next level the condenser mediate is split between the aplanatic and achromatic condensers that space corrected exclusively for either spherical (aplanatic) or chromatic (achromatic) optical aberrations. Common examples of these condensers are illustrated in figures 3 (achromatic) and Figure 4 (aplanatic). Achromatic condensers typically contain 3 to 4 lens elements and also are repair in 2 wavelengths (red and also blue) for chromatic aberration.


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The greatest level that correction because that optical aberration is incorporated in the aplanatic-achromatic condenser. This condenser is fine corrected because that both chromatic and spherical aberrations and also is the condenser of selection for use in vital color photomicrography through white light. A typical aplanatic-achromatic condenser is depicted in figure 5 (numerical aperture = 1.35). This condenser attributes eight interior lens facets cemented into two doublets and four solitary lenses.


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Engravings uncovered on the condenser housing encompass its form (achromatic, aplanatic, etc.), the numerical aperture, and a graded range that suggests the approximate adjustment (size) that the aperture diaphragm. Together we pointed out above, condensers with numerical apertures over 0.95 perform best when a drop of oil is applied to their upper lens in call with the undersurface that the specimen slide. This ensures the oblique light rays create from the condenser are not reflect from underneath the slide, however are directed right into the specimen. In practice, this can become tedious and is not typically done in regime microscopy, however is crucial when working at high resolutions and also for specific photomicrography using high-power (and numerical aperture) objectives.

Another important factor to consider is the thickness that the microscopic lense slide, i m sorry is as crucial to the condenser together coverslip thickness is come the objective. Many commercial producers sell slides that range in thickness between 0.95 and 1.20 mm v the most typical being an extremely close come 1.0 mm. A microscope slide the thickness 1.20 mm is as well thick to be provided with most high number aperture condensers that often tend to have actually a really short working distance. While this walk not considerably matter for regime specimen observation, the results can be devastating with precision photomicrography. Us recommend that microscopic lense slides be preferred that have actually a thickness of 1.0 ± 0.05 mm, and that lock be thoroughly cleaned prior to use.


Condenser light Cones

Study just how optical correction affect the size and shape of condenser irradiate cones.


When the objective is changed, for example from a 10X come 20X, the aperture diaphragm that the condenser must also be adjusted to administer a new light cone that matches the numerical aperture the the brand-new objective. This is done by turning the knurled knob ~ above the condensers illustrated in numbers 2-6. Over there is a little yellow arrowhead or index mark situated on this knob that indicates the loved one size of the aperture when compared to the straight gradation on the condenser housing. Many manufacturers will certainly synchronize this gradation to correspond to the approximate numerical aperture the the condenser. Because that example, if the microscopist has actually selected a 10X objective of number aperture 0.25, then the arrowhead would be placed next the value 0.18-0.20 (about 80 percent the the objective numerical aperture) ~ above the gradation enrolled on the condenser housing.

Often, that is not practical to use a solitary condenser with an entire range of missions (2X to 100X) as result of the broad variety of irradiate cones that must be created to match objective number apertures. V low-power missions in the variety 2X come 5X, the illumination cone will have actually a diameter in between 6-10 mm, if the high-power missions (60X to 100X) require a highly concentrated light cone only around 0.2-0.4 mm in diameter. V a addressed focal length, the is an overwhelming to attain this wide range of illumination cones through a solitary condenser.


In practice, this trouble can be resolved in numerous ways. For short power goals (below 10x), it might be vital to unscrew the optimal lens of the condenser in stimulate to to fill the field of view through light. Some condensers are produced with a flip-top top lens to accomplish this more readily, as portrayed in figure 6. Numerous manufacturers now develop a condenser i m sorry flips over totally when provided with low strength objectives. Other companies might incorporate auxiliary correction lenses in the light course for securing proper illumination with objectives much less than 10x. As soon as the condenser is used without its optimal lens, the aperture iris diaphragm is opened vast and the field diaphragm, currently visible at the ago of the objective, serves together if it were the aperture diaphragm. Flip-top condensers are produced in a range of configurations through numerical apertures varying from 0.65 to 1.35. Those condensers that have actually a numerical aperture value of 0.95 or less are intended for use through "dry" objectives. However, flip-top condensers that have actually a number aperture higher than 0.95 room intended for use through oil-immersion objectives and they must have a fall of oil placed in between the bottom of the microscopic lense slide and the condenser peak lens as soon as examining critical samples.

In addition to the common brightfield condensers disputed above, there room a wide range of dedicated models suitable to countless different applications. Table 2 perform a variety of different condenser configurations and the intended applications.


Substage Condenser Applications
CONDENSER TYPEBRIGHTFIELDDARKFIELDPHASECONTRASTDICPOLARIZING
Achromat/ AplanatN.A. 1.3⋅<10x~100x>
Achromat Swing-outN.A. 0.90⋅<4x~100x>
Low-PowerN.A. 0.20⋅<1x~10x>
Phase comparison AbbeN.A. 1.25⋅<10x~100x>
Phase comparison AchromatN.A. 0.85⋅<4x~100x>
DIC UniversalAchromat/Aplanat⋅<10x, 100x>⋅<20x, 40x, 100x>
Darkfield, dryN.A. 0.80~0.95⋅<4x~40x>
Darkfield, oilN.A. 1.20~1.43⋅<4x~100x>
Stain-Free AchromatSwing-Out N.A. 0.90⋅<4x~100x>
Table 2

From the data in Table 2, that is noticeable that substage condensers have a great deal of interchangeability among different applications. For instance, the DIC universal achromat/aplanat condenser is helpful for brightfield, darkfield, and also phase contrast, in enhancement to the primary DIC application. Other condensers have similar interchangeability. We will attend to various facets of individual methods that call for modified condensers in our ar on Specialized Microscopy Techniques. You re welcome feel cost-free to visit this interesting part of our Website for much more specific information about substage condensers.


Contributing Authors

Mortimer Abramowitz - Olympus America, Inc., 2 Corporate center Drive., Melville, brand-new York, 11747.

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Michael W. Davidson - national High Magnetic ar Laboratory, 1800 east Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.