This section contains a glossary of some terms associated with the construction and use of the light microscope. The explanations are offered in a simplified form so as to be useful for those new to the instrument. For more detailed explanations, see the literature listed by suppliers such as Savona Books.
Diagram - The basic parts of a traditional microscope:
A = Foot, B = Limb, C = Body tube, D = Mirror, E = Eyepiece, F = Rotating Nosepiece, G = Objective, H = Coarse focus, I = Fine focus,
J = Substage focus, K = Stage, L = Condenser, M = Diaphragm (L and M form part of the substage)
Glossary
Achromat
A lens or lens system which is partially corrected (two colours) for chromatic aberration. Ca apply to both condensers and objectives.
Apochromat
As an achromat but the lens/system is corrected for three colours.
Binocular microscope
A microscope with two body tubes allowing both eyes to be used for viewing the specimen.
This does not necessarily provide a 3D stereoscopic image - see Stereo microscope. The main advantage of the binocular instrument is more comfortable and relaxed vision, particularly important when using the instrument for protracted periods.
The 'standard' binocular instrument uses two eyepieces, but only one objective - hence the lack of stereo effect.
Body tube
A tube that forms the main part of the optical path - with an eyepiece at the end nearest the eye and an objective at the end adjacent to the object being viewed.
Bullseye condenser
A convex lens mounted on a stand or adjustable arm and used for concentrating light onto the specimen. A Victorian innovation.
Coarse adjustment
A means of moving the body tube and objective towards or away from the slide, to bring the specimen into rough focus
Compound microscope
An instrument consisting of a tubular body with an eyepiece at one end, an objective at the other, plus a stage for supporting the specimen and a Substage for adjusting the intensity of the illumination.
Condenser (Substage condenser)
A device with two or more lenses, held in the substage to concentrate the available light onto transparent specimens.
Cover slip (Cover glass)
A thin piece of glass (normally square or round) placed over the microcosmical specimen. Intended to help preserve the specimen it also forms part of the optical system and its thickness etc has to be taken into account when designing and using the instrument.
Darkground condenser
A condenser designed for darkground examination of the specimen. Light is prevented from passing through the objective aperture and the image is formed by the light scattered by the object itself. The image appears bright against a dark background.
Diaphragm
An adjustable (normally circular) aperture placed in the substage just below the condenser. I is used to control the intensity of the light passing into the condenser.
Eyepiece
The eyepiece, or ocular, is a lens system
which produces the final magnification, from the primary image formed by the objective.
Filter
Sometimes a filter is inserted into the optical path just below the condenser, so as to alter the colour or intensity of the light passing through the specimen.
Fine adjustment
A means of adjusting the focus to finer limits - is used after the image has been roughly focused using the coarse focus.
Foot
The base of the microscope.
Limb
The central part of the microscope which carries the main parts, such as tube, stage and substage.
Mechanical stage
A stage fitted with an adjustable
mechanism for holding and moving the slide - thus allowing precise positioning of the specimen.
Mirror
Most early microscopes were fitted with a mirror (flat on one side and concave on the other) for directing the light source into the condenser.
Monocular microscope
A microscope with a single body tube.
Nosepiece
Many microscopes are fitted with some form of rotatable nosepiece capable of holding two, three or more objectives. The nosepiece can be rotated so that one of the objectives is in line with the body tube.
Objective
The first part of the imaging system - placed close to the object. It forms the primary image.
Polarising microscope
A special form of microscope
designed for use with polarised light to examine specimens such as crystals and ore / mineral samples. It consists of the normal microscope components with the addition of a polariser, analyser and other specialised attachments.
Slide
A holder for the specimen - normally of glass and of a standard size and thickness. Some early slides were made of wood or ivory.
Slider
Before the use of glass
to produce slides (it was expensive in the 18th 19th centuries) specimens were usually mounted on small narrow 'sliders' made of bone or ivory. They normally held several specimens - one each in small circular holes. Solid objects were usually uncovered and transparent specimens were held between two thin pieces of mica..
Stage
A flat square or round plate fixed to the limb at right angles to the body tube - used to support the specimen or slide.
Stage clip
Most stages of early microscope were fitted with two spring clips to hold the slide in place. The position of the slide had to be adjusted by moving it with the fingers. More precise control is provided by a mechanical stage (see above).
Stereo microscope
A microscope that can produce two distinct
optical paths to give an erect image - allows the object to be viewed by each eye from a slightly different angle. The image has 'depth' thus providing stereoscopic perception of the object.
Stop
A fixed size aperture that can be placed in the light path between the mirror and the specimen. Sometimes found on cheaper instruments, particularly from the Victorian period (
takes the place of the diaphragm). The instrument would normally be supplied with two or more stops with different hole sizes.
Substage
Part of the microscope attached to the limb under the stage and which holds the condenser, diaphragm and usually a filter holder.
It can normally be adjusted so as to move it towards or away from the stage.
Wenham binocular microscope
An early form of binocular instrument introduced by Francis Wenham in 1860. The light from the objective is split using a single prism, placed just above the objective, and passed
into the two body tubes. The concept proved quite popular and many manufacturers used the design in their ranges.