Microscope Terms

 Microscope Terms:


Abbe Condenser:  A specially designed lens that mounts under the stage and is usually movable in the vertical direction.  It has an iris type aperture to control the diameter of the beam of light entering the lens system.  By changing the size of the iris and moving the lens toward or away from the stage, the diameter and focal point of the cone of light that goes through the specimen can be controlled.  Abbe condensers really become useful at magnifications above 400X.  The condenser lens system should have a numerical aperture equal to or greater than the N.A. of the objective lens being used. There are two types of condensers. One is a spiral type that you turn to move it up or down - typically found on entry level microscopes. The other is on a rack and pinion system and controlled with a condenser focusing knob. This type of condenser is crucial for laboratory grade microscopes. 

Achromatic lenses:  When light goes through a prism or lens, it is bent or refracted.  Some colors refract more than others and as a result, will focus at different points, reducing resolution.  To help correct this problem, achromatic lenses are used.  These lenses are made of different types of glass with different indexes of refraction.  The result is a better (but not perfect) alignment of some of the colors at the focal point, thereby giving you a clearer image. 

Arm:  The part of the microscope that connects the tube to the base.  When carrying a microscope, grab the arm with one hand and place your other hand under the base.

Articulated Arm:  A type of stand that holds a microscope body.  The stand clamps to a table and has a variety of motion in three dimensions. 

Base:  The bottom support of the microscope (see arm above).

Binocular Head:  A microscope head with two eyepiece lenses, one for each eye.  Generally this term is used in describing a high power (compound) microscope. All stereo microscopes have a binocular or trinocular head.

C-mount: The part that mounts the camera onto the trinocular port of a microscope. There are different power c-mount. The magnification of the c-mount should match the chip size of the computer.

Coarse Focus:  The large focus knob on the microscope. This should only be used to move the specimen into focus on the lowest power.

Coaxial Focus:  A focusing system that has both the coarse and fine focusing knobs mounted on the same axis.  Usually the coarse knob is larger and on the outside and the fine knob is smaller and on the inside. 

Condenser Lens:  A lens mounted in or below the stage whose purpose is to focus or condense the light onto the specimen.   The higher power objective lenses have very tiny diameters and require concentrated light to work properly.  By using a condenser lens you will increase the Illumination and resolution.  Condenser lenses are not required on low power microscopes.

Cover Slip:  A very thin square piece of glass or plastic placed over the specimen on a microscope slide.  When used with liquid samples, it flattens out the liquid and assists with single plane focusing.

Diaphragm:  Generally a five hole disc placed under the stage on a high power microscope.  Each hole is of a different diameter.  By turning 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.  A disc diaphragm is commonly found on entry level microscopes.

DIN Optics:  A German standard for the manufacturing of microscope lenses.  DIN lenses aren't particularly better than non-DIN but they will be interchangeable from one DIN microscope to another.  They are set to work with a 160mm tube length and have a uniform thread.  Most quality microscopes use DIN optics.

Diopter Adjustment:  This adjustment allows the users to compensate for the focal length of their eyes.  The way to correctly adjust this is to first close the eye over the eyepiece with the diopter adjustment and normally focus the microscope so that the open eye sees the image in focus.  Next, switch eyes (close the open eye, open the closed eye) and without changing the main focus knobs, focus on the image by turning the diopter adjustment only.  Now with both eyes open, the image should be clear with both eyes. This is the same procedure you would use when operating a pair of binoculars.

Dual Head:  A dual head is a head with two desperate eyetubes and eyepieces. There are two uses for a dual head. One is so that a teacher can quickly see what the student is looking at. The second is the second eyetube can accept a camera.

Eyepiece: What you use to look through the microscope. The most common eyepiece is a 10x eyepiece.

Fine Focus: The fine focus is used to fine tune the microscope to get the specimen into focus. This slightly moves the microscope stage. You should use the fine focus after using the coarse focus to focus on low power.

Field of View:  Sometimes abbreviated "FOV", it is the diameter of the circle of light that you see when looking into a microscope.  As the power gets greater, the field of view gets smaller. 

Fixed Arm:  A flex arm is used to hold a stereo microscope body. It has the ability to be easily manipulated into position.

Focus: Moving the specimen closer or further away from the objective lens to render a sharp image.

Head: The uppermost part of the microscope. The head accepts the eyepiece and is secured onto the top arm of the microscope. There are 3 categories of heads: monocular, binocular, and trinocular.

Illuminator: This is what provides the light to your microscope. LED is becoming the most popular type of illuminator.

Immersion Oil:  This is used what is used on oil immersion objectives, most commonly the 100x objective.

Interpupiliary Adjustment:  When using a stereo or binocular microscope there must be an adjustment for the distance between the viewers eyes.  A young child will have a small interpupiliary distance and an adult a larger one.  The eyepiece lenses will spread apart or get closer together to fit each individual.  This should be the first adjustment to make so that you are comfortably viewing the specimen with both eyes.

Mechanical Stage: This is what is used to penultimate the specimen around on the stage. A mechanical stage is higly recommended when using the higher power objectives.

Micrometer:  Also called a micron it is the metric linear measurement used in microscopy.  There are 1000 microns in a millimeter.  If something is 1.8mm long then it can also be expressed as 1,800 microns (or micrometers) long.

Monocular Head:  A microscope head with a single eyepiece lens. An entry level microscope will have a monocular head.

Nosepiece:  This is what hold the objectives. You rotate the nosepiece to engage the objective of your choice.

Numerical Aperture (N.A.):  This is a number that expresses the ability of a lens to resolve fine detail in an object being observed. To get the best possible image, you should have a condenser system that matches or exceeds the N.A. of the highest power objective lens on your microscope.

Objective Lens:  The lens closest to the object.  In a stereo (low power) microscope there are objective pairs, one lens for each eyepiece lens.  This gives the 3-D effect.  On a high power binocular model there is still only one objective lens so no stereo vision.

Oil Immersion Lens: The most common oil immersion lens is the 100x objective.

Parcentered:  This means when you change objectives the specimen in the center should remain in the center from objective to objective.

Parfocal: This refers to a microscope that requires only small fine focus adjustments when changing from objective to objective.

Pointer:  A pointer is typically found in the right eyepiece. It is used to help benchmark an area on your specimen.

Post Stand:  A type of stand used with low power microscopes.  It consists of a single post rising vertically from the base.  The microscope body can rotate about the post and also be moved up and down on it. 

Rack and Pinion:  The rack is a track with teeth and the pinion is a gear that rides on the teeth. This is the mechanism that allows most condensers to move up and down.

Rack Stop (or Safety Rack Stop):  This is what prevents the microscope from raising into the objective lens.

Resolution:  The ability of a lens system to show fine details of the object being observed.

Reticle:  A very tiny grid pattern inserted in an eyepiece lens.  It is used to make actual measurements of the size of objects seen through the microscope.

Ring Light:  Used on a stereo microscope it is on of the most common forms of illumination.

Semi-Plan Lenses:  Lenses are never perfect.  If you were looking at something perfectly flat, you might find that much of the center part of your field of view is in focus but out on the edges it is fuzzy and a bit out of focus.  Semi-plan lenses improve this deficiency by showing sharper images and less aberrations in the perimeter of the field of view.  They are better than standard achromatic lenses but cost quite a bit more.

Slide:  A piece of glass which the sample is mounted on. Typically a cover glass is placed over the sample.

Stage:  The part of the microscope that the slid is place on to be examined.

Stage Clips:  Found on entry level microscopes these are used to hold the slide into position.

Stage Plate:  A glass or plastic plate on a stereo microscope where the specimen is mounted.

Stereo Microscope: A low power microscope that provides a 3D image.

Sub-stage:  This is the area below the microscope stage.

Tension Adjustment:  This allows you to adjust the amount of torque require to turn the find focus knob.

Trinocular Head:  A binocular head with a port that allows a user to attach a c-mount to outfit the microscope with a camera.

Widefield eyepiece lenses:  These are wide diameter glass eyepiece lenses.  They offer the greatest field of view when looking at specimens. 

X:  An abbreviation standing for the amount of magnification. EX. 10x eyepiece . A eyepiece with ten times magnification.

R: An abbreviation referring to the retracting functionality of a microscope objective lens. Typically a feature of 40x and 100x objectives. The objective lens will retract when pushed against to prevent damage to the lens and slide.