Microscopes

Martin Microscope Company keeps a wide variety of new and used microscopes and accessories in stock.

There are many microscope websites out there that will display hundreds of different microscopes with no clear indication of what makes one better than another.  We take a different approach.  The microscopes and accessories we list on our website are not an exhaustive list, but rather are microscopes that we have used, serviced, and generally recommend.  As an independent company with many years of experience in microscopy, we are able to carefully select specific models from various brands at various price-points that we believe are the best in their respective classes.  We are a full-service microscope company providing sales, support, service, and even customized solutions.    View some of our custom projects here…

 

There are two main types of light microscopes:  COMPOUND and STEREO microscopes.  COMPOUND MICROSCOPES are so called because they are designed with a compound lens system.  The objective lens provides the primary magnification which is compounded (multiplied) by the ocular lens (eyepiece).  Visual information produced by compound microscopes are two dimensional, as opposed to those produced by stereomicroscopes which are three dimensional.  Most provide an image which is upside down and backward as compared to the actual orientation of the object.  Compound microscopes usually have several objectives in magnifications ranging from about 4x to 100x.  Eyepieces are commonly 10x resulting in total magnifications of 40x to 1000x (Objective x Eyepiece). Compound microscopes may be upright or inverted.  There are a variety of microscopy techniques available for compound microscopes, many of which are discussed below.  More on STEREOMICROSCOPES may also be found below.

- Brightfield 

BRIGHTFIELD TRANSMITTED LIGHT microscopes are the most common type of compound microscope.  These microscopes are the type used in biology classrooms and doctors’ offices.  The object to be inspected is normally placed on a clear glass slide, and light is transmitted though the object.  This makes the object appear against a bright background, hence the term Brightfield.

Blood1000x     Telia
Examples of Brightfield Microscopy:  Human blood cells (1000x); Telia spores (200x)

- Phase Contrast (PCM) 

TRANSMITTED LIGHT PHASE CONTRAST is an illumination technique which enhances the phase difference between the specimen and its surroundings.  Specimens which have a refractive index similar to their surroundings can be invisible in Brightfield, but are well defined in Phase Contrast.  Phase Contrast requires a special set of objectives with phase rings placed in the back focal plane of the objective.  A matching phase ring is placed in the condenser.  A Phase Turret condenser will usually have a Brightfield position as well as Phase positions to match each Phase objective.  Phase Contrast is normally used to examine unstained biological specimens.

MiteBF     MitePH1
Example of Phase Contrast Microscopy:  Brightfield image as compared to Phase Contrast image

- Differential Interference Contrast (DIC) 

TRANSMITTED LIGHT DIFFERENTIAL INTERFERENCE CONTRAST (DIC) is an illumination technique which, like Phase Contrast, enables specimens that have a refractive index similar to their surroundings to be visually differentiated.  This is an interference technique which relies on Polarized illumination.  Wollaston prisms placed in the condenser and in the back focal plane of the objective modify the normal extinction resulting from the crossed polarizers to create a 3D effect of the specimen’s surface.  A DIC Turret condenser will usually have a Brightfield position as well as DIC positions to match each objective.

ChironomidBF     ChironomidDIC
Example of Differential Interference Contrast Microscopy:  Brightfield image as compared to DIC image

- Epi-Fluorescence 

EPI-FLUORESCENCE, or Reflected Light Fluorescence is a technique in which light in a certain band of wavelengths is allowed to strike the specimen.  The specimen then absorbs this light energy and emits light of a longer wavelength.  Specimens may be autofluorescent or may be stained with a special fluorochrome.  Epi-Fluorescence was made possible with the development of the dichroic mirror which reflects certain wavelengths while allowing higher wavelengths to pass through.  A complete fluorescence filter cube will contain an excitation filter, a dichroic mirror, and a barrier filter.  Some filter sets are very common such as those for FITC (blue excitation) and TRITC (green excitation), and most of the fluorescence microscopes we have in stock have these cubes.  As a dealer for Chroma Technology, we can supply filter sets  for just about any fluorescence application.  For more information on fluorescence and custom filter sets see Chroma’s website. Epi-Fluorescence is often combined with Transmitted Light Brightfield, Phase Contrast, and/ or Differential Interference Contrast.

NervecellsFL     BicomponentFL
Example of Fluorescence Microscopy:  Nerve cells (400x); Bi-component fibers (200x)

- Polarizing (PLM) 

POLARIZED LIGHT is an illumination technique in which polarizing filters are placed above (Analyzer) and below (Polarizer) the specimen.  When these filters are engaged and crossed a black-out effect occurs called Extinction.  Specimens which are birefringent (having more than one index of refraction) will appear bright against the black background.  True Polarizing microscopes, often called petrographic microscopes,  will have a circular rotating stage, a centerable nosepiece, and a Bertrand lens for observation of conascopic images (interference figures).  Polarizing microscopes can provide quantitative information about the specimen.  They are used in geology for mineral thin sections, by textile and forensic sciences for fiber analysis, etc.  A specialized polarized light technique call Disperserion Staining is used for asbestos identification.  Simple polarizing filters can easily be added to ordinary Brightfield microscopes.  Doctors often use this technique for examination of gout crystals.

Mineral-POL Mineral-BF
Mineral cross section in Brightfield and Polarized light

- Reflected Light Metallurgical 

REFLECTED LIGHT METALLURGICAL microscopes are used to examine opaque specimens which will not transmit light.  Reflected Light is also called Incident Light or Episcopic Illumination (Epi for short).  The illumination is reflected off of a beam splitter – a half mirror where half the light is reflected and half passes through.  The reflected light travels through the objective lens, which in this arrangement acts as both a condenser and an objective, and strikes the specimen.  It is then reflected off the specimen back up through the objective lens, the half mirror, the head, the eyepieces, and finally to the eye.  Many of the microscopy techniques common to transmitted light microscopes are also available for reflected light microscopes, including Brightfield, Darkfield, and DIC.  Objectives on a reflected light microscope are usually corrected for use with specimens without a coverslip.  For some specimens a combination of transmitted and reflected light is ideal, so certain models will offer both types of illumination.  Inverted reflected light microscopes have the advantage of accepting larger specimens, and these specimens have to be flat on only one side.

Met-BF Met-DF Met-DIC
Capacitor cross-section in Brightfield, Darkfield, and DIC reflected light

STEREOMICROSCOPES 

STEREO MICROSCOPES, also called dissecting microscopes, are really two compound microscopes which focus on the same point from slightly different angles.  This allows the specimen to be viewed in three dimensions.  As opposed to compound microscopes, the image is upright and laterally correct (not upside down and backwards).  Stereo microscopes are relatively low power compared with compound microscopes, usually below 100x.  They can have a single fixed magnification, several discrete magnifications, or a zoom magnification system.  Working distance is much longer than with a typical compound microscope as well, allowing work to be done on the specimen while it is being observed through the microscope (hence the name “dissecting microscope”).  Many stereo microscopes are modular in design allowing a variety of stands, eyepieces, objectives, and lighting techniques to be implemented depending on the intended use.

ButterflyScalesCircuitBoardFlowerbug
Example of Stereomicroscope images: Butterfly Wing Scales, Circuit Board, Insect on Flower

 

COMPOUND MICROSCOPES:
– STEREOMICROSCOPES
– EDUCATIONAL MICROSCOPES
– BIOLOGICAL / MEDICAL MICROSCOPES
– RESEARCH MICROSCOPES
– INDUSTRIAL MICROSCOPES
– USED MICROSCOPES
– FEATURED ACCESSORIES