Microscope Guide
   
 Microscopes
      Microscope
A microscope is an instrument for viewing items that are too small to be seen by the unaided or nude eye. The examining of small objects using such a device is called microscopy. The phrase microscopic means miniature or very small.
   
   
  Commonly Used Phrases and Terms

TYPES OF MICROSCOPES

Compound
Constructed with two optical paths at the same angle. The compound microscope has two systems of lenses for greater magnification. The objective lens provides the primary magnification which is compounded (multiplied) by the ocular lens (eyepiece). Images produced by compound microscopes are two dimensional. This type of microscope is used to study very small specimens and requires the specimens to be mounted on a slide.

Stereo
Designed with two separate optical paths with two objectives and two eyepieces to provide slightly different viewing angles to the left and right eyes. In this way it produces a 3-D visualization of the sample being examined. The zoom provides different magnification and features an inversion system which allows the image to be viewed normally and right side up. This type features a large stage for closer viewing of the non-microscopic world like rocks, insects, flowers, and dissection specimens and does not need to be mounted on a slide.

Digital Microscopes
BARSKA’s digital microscopes are state-of-the-art integration of high quality microscope and a digital camera. Simply connect the microscope to the computer with the USB cord to magnify the object and view them on your PC screen and with option to save. Digital microscopes are great for educational purposes because several people can view the specimen at once, unlike a traditional microscope where one person can view at time.

POWER

Total Magnification
Total magnification is calculated by multiplying the magnification of the eyepiece by the magnification of the objective. 10x(eyepiece) x 4x(objective) = 40x Total Magnification

Zoom Magnification
Zoom models allow the user to zoom or change magnification continuously throughout the magnification range providing a low to high power range. For example, a 7x-45x microscope has the ability to magnify the object 7 to 45 times higher than an unaided eye.

WIDEFIELD EYEPIECE (WF)

An eyepiece with an achromatic doublet lens designed in such a way that it does not have to be limited to viewing only in its center, and the portion of the lens that allows non-distorted viewing is larger than a normal lens. This appears to the user as a bigger aperture or “hole” to look through. It therefore has the advantage of being easier to use and more forgiving of a user’s head movements. An eyepiece listed as WF10X/18mm would indicate it has a widefield achromatic doublet lens, 10x magnification and is 18mm in diameter

INTERPUPILIARY DISTANCE ADJUSTMENT

When using a binocular microscope with interpupiliary adjustment, there is an adjustment for the distance between the viewers’ eyes. A young child will have a small interpupiliary distance (IPD) while an adult will have a larger one. The eyepiece lenses will spread apart or get closer together to fit each individual.

MICROSCOPE HEAD
The head refers to the upper part of the microscope that contains the eyepiece tube and prisms.

Monocular
Contains one eyepiece

Binocular
Binocular has two eyepieces, one for each eye
 
Trinocular
The third vertical viewing port can be used with an eyepiece for a second person, such as an instructor. Or can be used with an adapter for video or still camera. 

ILLUMINATION

Transmitted and Oblique Illumination
Oblique lighting or top lighting shines down and reflects off opaque or solid specimens. Transmitted lighting or bottom lighting shines up through transparent objects. Not all microscopes will have these types of illumination.

Mirror
Mirrored illumination is a simple and inexpensive lighting system that uses light from an external source (in direct sunlight, lamp etc) and reflects it upward to the condenser/specimen from a mirror located below the stage.

Fluorescent
Fluorescent illumination provides a cool bright light. Ideal when viewing slides for long periods or studying live cellular specimens. 

Halogen
Halogen illumination provides the very brightest illumination, but tends to give off heat.

DIAPHRAGM

Generally a five-hole disc placed under the stage on a high power microscope. Each hole is a different diameter. By rotating it, you can vary the amount of light passing through the stage opening. This will help to properly illuminate the specimen and increase contrast and resolution. The diaphragm is most useful at the higher powers.

WORKING DISTANCE

This is the distance between the specimen or cover slip and the objective lens. On compound microscopes that use slides, the stage is adjustable allowing the user to zoom in or out of an image. On stereo microscope the stage is fixed.

ADJUSTMENTS

Coarse Focus
This is the rough focus knob on the microscope. You use it to move the objective lenses toward or away from the specimen. Generally use the coarse focus first to get close then adjust the fine focus knob for fine tuning.

Fine Focus
This is the knob used to fine tune the focus on the specimen. It is also used to focus on various parts of the specimen.