Glossary

It should be pointed out that many of these terms have a much broader meaning than what is described here. For the purposes of this document I will define these terms as they apply to amateur light microsopy.

Achromatic
This means that different colors focus at the same distance. When lenses are not achromatic, different colors focus at slightly dfferent distances. This makes it impossible to get a precise focus. This also causes the colored fringes charactheristic of a "toy" microscope and other low quality optical instuments. All lab quality optics are achromatic, and may have other characteristics as well, such as Plan or SHC.

AO American Optical
A company that made optical instruments for many years, also known as Spencer and AO/Spencer. The higher end AO series 10 microscopes sold new for about $800 to $1500 in the 60s and early 70s. Some of these are still in use at doctor's offices, vet clinics and various labs. They are also very popular among hobbyists and can often be found on eBay.

B.F. Bright Field
This is the the normal mode of Substage lighting in which the field, or empty area, around the subject is bright, ideally bright white. See Dark field.

Binocular Microscope
This describes a microscope with two eye pieces arranged so that you can look into it with both eyes. Stereo microscopes will be binocular but binocular microscopes are not necessarily stereo. Note that if the second eye piece is not arranged so that you can look into both at the same time (off at an odd angle) it is usually called a "multiview" or "teaching" microscope.

Biological Microscope
This describes a microscope with high magification, usually with several objectives on a rotating turret. Also commonly known as a compound microscope.

Canada balsam
Canada balsam aka "Canadian balsam" is mountant derived from the resin of the balsam fir tree common in Canada. Usually the resin was dissolved in xylene. Though it has fallen out of favor in recent years, largely replaced by synthetic alternatives, it was the standard mountant used for making permanent slides for many years. Most older "antique" slides sought by collectors were prepared using Canada balsam.

Though it didn't crystalize, thus preserving its optical properties, it did tend to yellow over time, giving older slides that distinct yellowed appearance. Some microscopists still prefer Canada balsam, not trusting modern synthetic mountants despite their many advantages, but most gave it up long ago or never used it in the first place.

Coaxial Fine Focus
A coxial fine focus is located on the same axle as the coarse focus and is capable of adjusting over the entire range of focus. The main advantage to coaxial fine focus is that it can reach the focal point no matter where the coarse focus is set. If the fine focus knob is on a seperate axle it will usually have a limited amount of movement and if it can't reach the focal point you will have to re-center the fine focus, re-adjust the coarse focus, then re-adjust the fine focus. That can be a real pain! It isn't surprising , then, that coaxial fine focus is a coveted feature.

Color filters
Color filters are often used in a special filter holder attached to the condenser. They can be used to add additional contrast to specimens that may have different absortion rates for different colors of light.
Filters can also be used to correct the color bias of the light source. The yellowish color of a halogen light, for example, can be corrected with a blue filter.

Compound Microscope
Literally this means a system with 2 or more lenses or sets of lenses. This usually refers to a biological or high power microscope, as opposed to a stereo other low power microscope. This term is not entirely accurate, since most stereo and other low power microscopes also have both ocular and objective lenses.

Condenser
This is a device that "condenses" or focuses the light. Special types of condensers are used for Dark Field and Phase Contrast work. Most condensers have a filter holder for color filters or perhaps a polarizer.

Cross Polarization
This is a specialized technique where two polarizers are used, one above the stage and one below, oriented in such a way so as to be 90 degrees out of phase. This cuts off nearly all the light when no specimen is present. When a spcimen is inserted in the light path it depolarizes the light, generating distinctive color patterns. Differences in structure disrupt the patterns, so it has been used to detect tampering in amber and translucent mineral specimens, and to give a visible structure to liquids such as beer, and chemicals such as testosterone.

C.S. Cross Section
This describes a thin slice that is cut across an object thus giving a flat section that is fairly translucent, and thus ideal for microscopic examination. The shape will be a 2 dimensional version of the orginal shape. Thus a solid cube would become a solid square, a hollow cube would be a hollow sqauare, a rod would be a solid circle and a tube wold be a hollow circle. If you look at the top of a stump from a tree cut straight across, you'll see what a cross section of a tree would look like.

D.F. Dark Field
This describes a technique used with substage lighting where light is prevented from entering the lens directly, thus only light which is scattered by the specimen is visible. This can be accomplished with a special dark field condenser or with a dark patch placed somewhere in the light path. Objects illuminated in this fashion seem to glow. This gives unique contrast characteristics to certian translucent subjects, but , like Bright field, works only with translucent subjects. For opaque objects, Super Stage lighting, also known as epiluminescence is used.

Epi Fluorescence
This is a specialized form of super stage lighting which uses a special lighting fixure mounted on the head of the microscope along with special filters and special objectives. The filters are "color exicting", causing the specimen to glow a color different from the color of the filter, similar to the way some objects glow in visible colors under UV. Usually the specimen is prepared with special dyes to make things even more exciting. These dyes fade when exposed to light, limiting the number of times the specially stained specimen can be used with this technique. The images produced with this technique are very impressive! This is an advanced and very expensive technique rarely used by amateur microscopists.

Epi Luminescence
This is a form of super stage lighting which uses a special lighting fixure mounted on the head of the microscope along with special objectives that have openings which allow light to shine through. This is the lighting technique used in Metalurgical Microscopes.

Eye Piece
Also known as "ocular", the eye piece is the part of the microscope that you look into. The power of the eye piece is multiplied by the power of the objective to give the total magnification. Most Lab quality binocular microscopes have interchangeable 10X and 16X lenses. Thus, a 40X objective can give either 400 or 640 power depending on which eye piece is used.

H&E Hematoxylin and Eosin
Histology specimens are often stained with a combination of Hematoxylin and Eosin. Different tissues will have different reactions to these two stains, mainly dependant on ph, and, as a result, are stained red, pink, blue, purple or very dark purple, almost black depending on their afftinity for one or both of these stains. When H&E stained slides are examined with the unaided eye they tend to have a pinkish purple appearance.

Hay infusion
A hay infusion is a means of obtaining a rich sample of microbes for microscopic study. The classic hay infusion involves adding dry, sometimes boiled, grass to a sample of pond water to serve as food for bacteria which in turn are consumed by the microbes, thus greatly increasing their density.

Another version of a hay infusion is to add water to a sample of dried manure, moss, aged vegetable matter, etc. to see what microbes are present.

Where no pond water or other souce of mature standing water is available grass and soil can be added to dechlorinated tap water to culture microbes present in the soil or as cysts. This will often allow observation in a wide variety of organisms such as colpoda, paramecia, amoebas, bdelloid rotifers, nematodes, vorticella, diatoms, euplotes, etc. If the culture is exposed to light various types of algae may grow, adding to the richness of the culture.

Histology
Histology is the study of tissue, specifically thin layers of animal or plant tissues mounted on a slide and usually stained for study under a microscope. A subset of this discipline is known as Pathology, which specifically studies diseased or othewise abnormal tissues. See Pathology for further discussion of this.

Histomount™
Histomount™ is a brand of modern synthetic mountant designed for use in histology, hence the name. It can be thought of as a modern equivalent of Canada Balsam, but it doesn't yellow over time.

Histomount™ produces museum quality slides which will last for years, possibly even centuries, but it does require a great deal of specimen preparation for good results. Like Canada Balsam, it does require a long time to harden, so slides prepared with it are not available for immediate use.

Because it contains Xylene, it has a fairly high toxicity and is highly flammable, requiring handling precautions that make it unsuitable for use by amateurs.

Hydromount™
Hydromount™ is a brand of modern water based sythetic mountant which uses glycerin instead of xylene. Thus no clearing agent is needed, greatly simplifying specimen preparation. Specimens mounted with Hydromount™ are not considered museum grade and can be expected to last a few years, rather than decades or centuries. Because it is water based, it can be dissolved in warm saline, thus allowing further preparation of the specimen.

Because of its low toxcity and flammability, only ordinary common sense precautions are required for its use, and no hazardous material surcharge is required when it is shipped. Thus, it could be considered suitable for use by reasonably skilled amateurs.

The better safety characteristics, coupled with the easier specimen preparation requirements and faster drying time mean that Hydromount™ could potentially be used in some field environments, to prepare slides that could be given a preliminary examination using suitable equipment and saved for more thorough lab examination later.

Immersion oil
This is a special type of oil such as natural cedar oil or any number of modern synthetic oils used with oil immersion objectives. The Numerical Aperture of immersion oil is greater than n.a. of air so using oil between the lens and the coverslip elimiates air in the lightpath and preserves the resolving power of the lens, thus giving a clearer image when using lenses with n.a. greater than 1. Oil is sometimes used between the condenser and the slide as well. Only objectives specifically designed for immersion oil can be used with it.

Oil immersion lenses can be used dry and will generally give a usable image, but the improvement gained by using oil with these lenses is significant. Use of oil adds additonal steps when looking at different parts of the specimen, and complicates changing powers since dry objectives can be easily fouled by oil.

Because they are designed to be immersed in a shallow pool of oil, oil immersion lenses are specially sealed to prevent intrusion of oil into the interior of the objective and will also have a very short working distance, even shorter than a high power objective would otherwise have. Great care must be used to clean both the slide and the lens after oil is used. Though modern oils are designed to not harden, they tend to trap dust, forming a very grimy coating.

L.S. Longitudinal Section
This is a thin slice taken lengthwise. This is good for showing the long structural cells in a plant stem.

L.W.D. Long Working Distance
This is a special purpose objective specifically designed to have a longer working distance than a similar lens would otherwise have. This could allow a wider range of focus over a thick specimen and reduces the chance of the lens contacting the slide. This also makes it easier to use superstage lighting with a microscope that doesn't have built in provision for it. These objectives are not common and are unlikely to be used by amateurs.

Mechanical Stage
This is a special stage, built in or added on, that moves a specimen around and is controlled by knobs. It replaces the slide clips used on a standard stage. Mechanical stages give much smoother and more precise control than what could be achieved by moving a slide by hand, and the use of a mechanical stage is generally considered essential at powers greater than 100X and useful at lower powers. Graduated mechanical stages can be used , along with calbration slides, to make fairly accurate measurements, and can also be used to "map out" a slide to go back to a particular section later.

Mechanical stages can have low level controls , beneath the stage, or high level controls, above the stage. Low level controls are easier to access and are typical of built in mechanical stages. High level controls more more diffcult to reach because the stage and objectives tend to get in the way. High level controls are more typical of attachable, or added on mechanical stages that are mounted on top of a standard stage.

Metalurgical Microscope
This is a microscope fitted with a lighting fixture on the head and special objectives featuring openings that allow light to shine through the outer rim and onto the object. These special "scopes" are called this because they are often used with metal specimens though they work well with other opaque objects such as mineral specimens and whole, sometimes live, insects. They are usually limited to a maximum of 400 power. These are specialized microscopes that are often quite expensive but some models sell for less than $1000.

Micro Potography, aka microphotography
This is photography through a microscope, often with the aid of the photo port on a trinocular microscope. This is done using a variety of optical devices. Contemporary users most often do it using a dedicated microscope camera though devices such as film cameras and small video cameras were frequently used in the past.

This is a very popuplar way to document observations made through a microscope as it is usually easier than drawing by hand and generally gives better results.

The image quality of modern digital microscope cameras, coupled with their fast frame rate as well as their availability and low cost often makes direct optical examination unnecessary. Indeed, many current microscopists use their screens almost exclusively rarely if ever bothering to look through the eyepiece. Since the instrument is already focused and adjusted for the camera, a screen capture or video is just a keystroke away and documentation is easier than ever before.

Microtome
A microtome is a device used to make thin slices (sections) of a specimen.

Monocular Microscope
This describes a a microscope with a single eyepiece. Most "toy" microscopes are monocular, but, though quality microscopes are more often binocular, monocular microscopes are not necessarily toys.

Mountant
This is a substance used on a permanent slide to hold the coverslip in place and to fill the space between the specimen and the glass, removing air from the optical path.

Canadian Balsam is the classic mountant, though there are many synthetic alernatives available today. Canadian Balsam was used to make museum grade slides, but tended to yellow over time. Water soluable mountants require less specimen perparation and are noted for low toxicity but slides thus prepared are not considered museum grade and will only last about 10 years. Museum grade mountants last many years but require more specimen preparation and many are noted for high toxicity and high flammability, but don't yellow over time.

N.A. Numerical Aperture
The technical definition involves angles and refraction and is kind of hard to grasp if you're not a physicist. What it amounts to, from the view of the amateur microscopist, is that a given objective lens can deliver a clear image at a magnification at about 1000 times the numerical aperature.

So a 40X lens with a numerical aperture of .64 could deliver a clear image at 640X. That's why eye pieces ae usually limited to 16X (there are other reasons as well) A 100X objective lens may have an N.A. of 1.3. Air has a numerical aperture that is slightly less than 1, so for magnificatons of 1000X or more you must not have any air between the subject and the lens, if a clear images is to be achieved. That's why you need a good mountant and an oil immersion lens and you have to use immersion oil to get a good image at 1000X+.

Objective lens
This is the lens that is closest to the object being examined. Changing powers usually means changing the objective lens, most often through use of a rotating turret.

Objective lenses are one of the more crtical parts of a microscope and come in a number of varieties. Some special purpose objectives cost more than an entire microscope equipped with standard objectives!

Oblique lighting
This is a lighting method where light comes in at an angle instead of directly underneath. This causes shadows and variation of brightness at different depths, thus highlighting the 3 dimensional aspects of the specimen, though the resulting images are not actually "3D" or stereoscopic. In microscopes equipped with a mirror, this can be accomplished by adjusting the angle of the mirror. In miroscopes with direct lighting this can be accomplished by using a dark patch beneath the condenser then adjusting the position of the patch and the elevation of the condenser to achieve the desired effect. Often it is possible to go from oblique lighting to darkfield by simply adjusting the elevation of the condenser and leaving the dark patch in the same position.

O.S. Oblique Section
This is a thin slice taken at an angle, resulting in a flat section that shows aspects of the specimen at different depths. This is also known as a diagonal section.

Ocular - see eye piece

P.C. Phase Contrast
This technique gives better contrast on unstained specimens and can show as much detail on unstained specimens as on stained specimens and sometimes even more. It gives live protozoans a really "cool" look. It works by making different phases of light appear as different shades of light.

Phase contrast can be done with a PC kit or with a dedicated PC microscope. It requires special objectives with an internal ring and a special condenser with a matching ring. Since different power objectives require different sized rings, a seperate condenser is needed for each power so switching powers requires changing condensers or using special revolving turret condenser. This is considered an advanced and somewhat expensive technique, used by more advanced amateur microsopists.

Parfocal
This means that different objective lenses are in focus on the same setting of the focus knob. The objective lenses of a properly adjusted lab quality micoroscope will be parfocal, though slight adjustment is often needed when switching to higher powers since the focus is more critical. A photo tube in a trinocular microscope can be adjusted to be parfocal with the eye pieces, but often at only one level of magnification.

Pathology
Pathology is a branch of histology that specifically involves the study of diseased or othwerwise abnormal tissues. Though this most often involves human tissue, it can also involve animal and even plant tissue. This can be used to study diease in general and also has the more practical application of diagnosing and/or documenting the condition of a patient. Thus, pathology slides are often found at doctor's and even vet's offiices, as well as at morgues and these are the sources of many of the pathology slides found on eBay. Other slides are produced by commercial labs and are usually intended for use by researchers.

Pathology slides are most often stained using H&E and many workers use this technique exclusively. Thus, the distinctive color patterns produced by this technique are often associated with pathology slides.

Plan
With Most lenses the focus varies across the width of the lens, so if an obeject is in focus when it is centered, it may go out of focus if moved toward the edge. Likewise, a perfectly flat object may be in focus in the center of the field and out of focus toward the edges. A plan objective lens gives a flat field across at least 95% ot the width of the field of view. Plan objecives are considered premium objectives and a set of plan objectives may cost several hundred dollars.

Some micrcoscopes are equipped with SemiPlan objectives, with fields that are not completely flat, but are flatter across more of the field than regular achromatic lenses. These have fallen out of favor in recent years because their over all optical quality is generally not what would be expected, causing some dealers to drop them from their line.

Reduction lens
This refers to a special lens, used with a digital microscope camera, with a magnification of less than one, usually .4 or .25 X.

Without the reduction lens a microscope camera will have an effective magnification of 25-40X depending on the size of the image sensor, the smaller the sensor, the higher the effective magnification. This resuls in a field of view much smaller than what is seen through a 10X ocular and may result in an effective magnification greater than what would be justified by the numerical aperture of the objective lens, which results in a significant loss of image quality. Also, the objectives will not be parfocal, thus large focus adjustments are necessary when changing objectives.

With the reduction lens, the magnification is close/identical to a 10x eyepiece, giving roughy equivalent field of view and, in most cases, better clarity, resulting in much sharper images, especially when using 40X and 100X objectives.

The one exception is when using a 10X objective. A 10X objective typically has a numerical aperture of .25 which gives a clear image at 250X thus, with the larger image sensors a clear image can be obtained without the reduction lens. In fact, the lack of a lens other than the objective gives even better image quality so images taken with a 10X objective at 250X are not only more magnified but actually sharper than those taken at 100X with the same setup, the only difference being that no reduction lens is used. Indeed, many amateur microscopists have found that their sharpest images ever taken are at 250X with just the bare sensor and a 10X objective, and the magnification is perfect for many "pond critters".

Reverse Nose Piece
This is a nose piece, turret, designed so that the unselected objectives point to the rear rather than to the front. This makes it easier to change slides since the unselected objectives don't get in the way.

Section
A section is a thin slice taken out of a specimen which can be mounted on a slide and observed with a microscope. Sections are made extremely thin so that they will be fairly translucent and will be observable over a narrow range of focus. Note that even the thinnest sections have some depth, so even well prepared slides will require focus adjustments when different parts of the specimen are viewed. Sections intended for observation with high power objectives, particularly oil immersion objectives, must be especially thin so that it is possible to bring all aspects of the specimen into focus.

Different kinds of sections such as cross sections, oblique sections and longitudinal sections, can be made to show different aspects of the specimen. In slide descriptions these are often shown as abbreviations, i.e., cs, ls, os, etc.

Serial Cross Section
A serial cross section is a prepared slide containing a number of cross sections from the same specimen taken at different depths, allowing different apsects of the specimen to be studied. In many cases the entire specimen will be sectioned and included on the slide. Chicken embryos at various stages of devlopment are popular subjects for this treatment.

SHC Super High Contrast
This is a type of objective lens that is not as common as standard achromatics or Plan objectives. These objectives give higher contrast images, bringing out more detail, especially on unstained specimens.

Slide
A slide is a rectangular piece of glass on which a specimen is mounted for microscopic examination. Slides can be purchased blank or as prepared slides with specimens already mounted and stained, ready for examination under the microscope.

Stain
Stains are dyes used to darken or "stain" a specimen to improve conrast and bring out details that might not otherwise be visible. Exessive staining can actually have the opposite effect, hiding details rather than enhancing them, esecially when used with digital cameras.

Common stains incude hematoxylin and eosin which are often used together on histology specimens, staining some structures red, some blue, some purple. Other common stains include Methylene blue, Carmine, Methyl green, etc.

Stereo Microscope
A microscope with dual objectives and dual eyepieces thus rendering both a right and left eye veiw, allowing objects to be seen STEREOscopically (in "3D"). These are often called "dissecting" microscopes because of their wide use in specimen and slide preparation. They are also used called "inspecton" microscopes and are often used in a variety of other fields such as electronics and medicine, and have even used by mothers to aid in the removal of splinters! Note that though stereo microscopes are usually low power, not all low power microscopes are stereo.

Sub Stage lighting
This the normal lighting method used with high power aka "compound" or "Biolocical" microscopes, in which light from below the stage shines through the subject. This is also known as "light transmission microscopy". This is used in conjunction with various techniques such as Bright Field , Dark Field, cross polarization, Phase Contrast, etc.

Super Stage lighting
This is the normal lighting method used with Stereo and other low power microscopes. It is used with opaque objects, and when it is used with opaque objects on a slide the field is dark, similar to when Dark Field is used with translucent objects. With high power microscopes the light comes down at an angle and while it works well at lower powers it is difficult or impossible to use at high powers unless a special microscope is used that has a lighting fixture mounted on the head and special objectives that allow light to shine through special openings, such as a metalurgical or Epi Fluorescence microscope.

Teaching microscope
Also known as a "multiview microscope", this is a microscope with one or more extra eypieces, or even exra binocular heads, so that two or more people can look into the microscope at the same time. These can be either biological or stereo microscopes. With the wide availability of projection and video devices that enable group viewing, these microscopes aren't as popular as they used to be, but many can be found for sale on eBay.

T.S. Transverse Section
This is essentially the same as a cross section, but specifically accross the vertical axis.

Trinocular
This describes a microscope with a speial third optical port which usually points straight up. The third port is used for an optical device, usually a still or video camera. This is often called a "photo tube" and, depending on the configuration, may be used with a film or digital camera, a dedicated microscope camera, or perhaps a video security camera.

W.D. Working Distance
One of the specs of an objective lens, along with power and numerical aperture. The Working Distance describes the distance between the subject and the lens at which the lens is focused. Lower power lenses have a longer working distance, higher power lenses have a shorter working distance. In a lab quality microscope the lenses are designed so that, when the instrument is properly adjusted, all objectives will be in focus at the same settng of the focus knob. Note, however, that higher power objectives have a more critical focus than lower powers, so slight adjustment of the fine focus knob will often be necessary.

Well slide
A Well slide, also known as a concavity slide is a slide with a shallow depression. This allows for a larger amount liquid to be placed on the slide, thus allowing a sample of pond water, hay infusion, etc. to remain liquid longer, and giving "pond critters" more freedom of movement. Well slides are often used when observing hay infusion samples. Sometimes glycerin or some similar substance is used to seal the edges, thus slowing evaporation.

Well slides are most often single concavity, but double and triple concavity slides are also available. Because they are more expensive than plain slides, they are more likely to be cleaned and reused by microscopists who habitually use plain slides only once.

Wet mount
When a temporary slide is prepared usually a few drops of water will be added to the specimen before it is covered with a coverslip. The water fills in the space between the specimen and the coverslip, thus providing a more consistent light path and giving a clearer image. This is known as a "wet mount" and is considered the standard method for preparing temporary slides of both whole mounts and sections.

The water also helps to spread out granular or powdered specimens so that they are not clumped together, making observations of individual particles much easier.

W.F. Wide Field
This refers to the viewable part of the eyepice or Ocular, a Wide Field eye peice allows you to back off from the eye piece a bit more and so it is possible to wear eyeglasses while using a microscope. This comes in handy when people with varying degrees of nearsightedness, farsightedness, etc. are alternately looking into the same microscope without using some kind of video or projecton attachment.

White balance
This refers to a setting, in an imaging device, that automatically corrects the color balance to make the current field white. The idea is that if white light is seen as white, the other colors will also look correct.

When an imaging device used with a microscope has a properly set white balance color filters that correct for the "yellowness" or other color bias in the light source become unnecessary and can be removed for maximum lighting effeciency.

W.M. Whole Mount
This term is a little misleading. It means that it is not sliced or sectioned and thus retains the original thickness of the object. A whole mount of a butterfly wing, for example, would not necessarily be an entire butterfly wing, but usually a small piece that is as thick as the orginal rather than a thin slice of it.

XY movement
This term is used in reference to a mechanical stage. X refers to the right and left movement. Y refers to forward and backward movement, thus mechanical stages are sometimes referred to as "XY" mechanical stages (is there some other kind?) or simpy as XY stages. In case you're wondering, "Z" would be the focus, i.e. up and down movement.

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