Microscopes
Table of Contents WHAT IS A MICROSCOPE ? ............................................................................................................................................. 3 WHAT IS MICROSCOPY ?................................................................................................................................................. 3 WHO INVENTED THE MICROSCOPE ? .........................................................................................................................
Microscopes What is a microscope ? A microscope is a high precision optical instrument that uses a lens or a combination of lenses to produce highly magnified images of small specimens or objects especially when they are too small to be seen by the naked (unaided) eye. A light source is used (either by mirrors or lamps) to make it easier to see the subject matter. What is microscopy ? Microscopy is the use of a microscope or investigation by a microscope.
Who invented the microscope ? There is no one person who invented the microscope as several different inventors experimented with theories and ideas and developed different parts of the concept as they evolved to what is today’s microscopes. About 1590 two Dutch spectacle makers, Zaccharias Janssen and his son Hans, experimented with a crude concept of a microscope that enlarged objects 10x to 30x or so.
Blood Smear Schematic Mite Eggs Normal will become extraordinary when looking through a microscope. You will find that almost everything (alive or that was alive) consists of components called cells and they take on a fabulous view at the cellular structure – like your own blood, molds, yeast, and bacteria. You can observe prepared slides or prepare your own. You can spend hours examining a drop of pond water and observing the enormous amount of life within it.
Education Medical & Research Science Molecular Structure Types of Microscopes The majority of microscopes are called light (bright field) microscopes since they rely on light to observe the magnified image of a specimen or object. Within this category are two main categories – (1) compound (high power microscopes), and (2) stereo or dissecting (low power microscopes). Compound Microscope This is the most common type of microscope. It can also be referred to as a biological or research microscope.
Compound Microscope Compound refers to the fact that in order to enlarge an image, a single light path passes through a series of lenses in a line where each lens magnifies the image over the previous one. In other words, one light path with multiple lenses equals a compound microscope. The image is seen by the observer as if it were only 10” (250mm) from your eye.
Stereo Microscope There are two separate light paths (as opposed to a single light path in a compound microscope) which produce a true stereo, three dimensional (3-D) image of the specimen or object. Within the objective lens you will find two lenses (one for each path of light) side-by-side. The optical design parameters of a stereo microscope limit its 3-D effects to low powers only.
Fluorescence – These microscopes use an illumination method that is used to locate fluorescently tagged material (protein, enzyme, genes) by exciting the specimen with one wavelength of light in hopes that the fluorescence will appear by emitting a light at a different wavelength. Metallurgical – A microscope that is used for identification, inspection, and analysis of different metals and alloys.
1. Eyepiece 2. Eyepiece Tube 3. Coarse Focus Knob 10. Arm 12. Nosepiece 11. Fine Focus Knob 4. Objective Lens 9. Safety Rack Stop 5. Specimen Stage 8. Stage Holder Clamp 6. Illumination Mirror 7. Base Compound Microscope 1. Eyepiece & Rubber Eyecup 2. Diopter Ring 15. Pillar Stand Safety Screw 3. Head 14. Pillar Stand 4. Binocular Head Tension Screw 5. Objective Lens Housing 13. Pillar Stand Locking Knob 6. Specimen Slide Holder Clips 12. Focus Knob 7. Stage Plate 11. Top Light Illuminator 10.
Stereo Microscope Objective Lenses Objectives for compound microscope Objectives Mounted Objective on Stereo Microscope The objective lenses are the most important components of microscopes and thus will be discussed in greater detail here. Their basic function is to gather the light passing through the specimen and then to project the image up into the body of the microscope. Then, the eyepiece lens system further magnifies the image for your eye to see.
DIN (Deutsche Institut Fuer Normung) standard objectives are the most popular in international standards which dictates the design capability of the objectives. DIN standard objectives from one manufacturer can be used in another manufacturer’s compatible microscope. The standard refers to the 45mm parfocal (explained below) distance and RMS standard 33mm thread for the objective. The 45mm distance is the measurement from the mounting hole in the objective nosepiece to the point of focus on the specimen.
objective lenses have very tiny diameters and require concentrated light to work properly. A basic condenser is fixed in place. A moveable and more precise and more expensive condenser is the Abbe condenser. It usually can be moved up and down vertically, regulating the amount of light from the illuminator. It mounts under the stage and usually has an adjustable iris type aperture to control the diameter of the beam of light entering the lens system.
is needed then use the concave side. These methods are the least expensive illumination methods but it can be difficult to direct the light source for proper illumination. The more expensive and common illumination is by using built-in or attached light sources using bulbs or lamps that provide direct and intense illumination.
Focus Systems A focus control allows you to adjust the focus of the microscope. Every microscope includes a focusing control (knob) for quick (coarse) focusing of the image. More expensive compound microscope models include a coarse (quick) and fine focusing control. The fine focus is particularly advantageous in high power applications and required for 400x and higher but is not available on stereo microscopes since they are only low power.
Binocular Head Trinocular – this is a microscope with a binocular head for viewing and an additional port that can be used for a third eyepiece for a second person (or teacher) to use or it would be used for various photo applications. On many microscopes, the amount of light can be adjusted (from 30% to 70% or so) for the third port. Binocular heads contain prisms carrying light rays from the objectives to the eyepieces.
the eyepiece (tube) lens. The tube length is a fixed measurement in millimeters of the distance from the objective shoulder to the seat of the eyepiece which is typically DIN 160mm or 170mm (except on introductory microscopes) where the focused image forms. This distance governs the interchangeability of optical components. Tube Lens At the bottom of the eyepiece tubes is a tube lens.
Depth of Field – how much depth of field is a function of the objective lenses and means the farthest and nearest points in the field of view are in simultaneous sharp focus. Low magnification objectives have more depth of field than high magnification objectives. Depth of Focus – means the farthest and nearest points in the film plane (photomicrography) or the CCD plane (video microphotography) which are simultaneously in focus.
Two extremes are the Plan optical microscopes which provide incredible performance with the least amount of aberrations on a microscope and microscopes with plastic optics which give you the most aberrations and the worst performance. Chromatic Aberration – is a failure to bring light of different wavelengths (colors) to a common focus. You may see color fringes or halos especially at the edges of the field of view or around the specimen you are looking at.
