Microscopy

img

Microscopy

Introduction

A microscope is an instrument that makes an enlarged image of a small object, thus revealing details too small to be seen by the unaided eye. The most familiar kind of microscope is the optical microscope, which uses visible light focused through lenses.

Brief History

Historians credit the invention of the compound microscope to the Dutch spectacle maker, Zacharias Janssen. The twentieth century saw the development of microscopes that leveraged nonvisible light, such as fluorescence microscopy, which uses an ultraviolet light source, and electron microscopy, which uses short-wavelength electron beams. These advances led to major improvements in magnification, resolution, and contrast. By comparison, the relatively rudimentary microscopes of van Leeuwenhoek and his contemporaries were far less powerful than even the most basic microscopes in use today. In this section, we will survey the broad range of modern microscopic technology and common applications for each type of microscope.


The Functions & Parts of a Microscope

EyePiece Lens: the lens at the top that you look through, usually 10x or 15x power.

Tube: Connects the eyepiece to the objective lenses.

Arm: Supports the tube and connects it to the base.

Base: The bottom of the microscope, used for support.

Illuminator: A steady light source (110 volts) used in place of a mirror. If your microscope has a mirror, it is used to reflect light from an external light source up through the bottom of the stage.

Stage with Stage Clips: The flat platform where you place your slides. Stage clips hold the slides in place. If your microscope has a mechanical stage, you will be able to move the slide around by turning two knobs. One moves it left and right, the other moves it up and down.

Revolving Nosepiece or Turret:This is the part of the microscope that holds two or more objective lenses and can be rotated to easily change power.

Objective Lenses: Usually you will find 3 or 4 objective lenses on a microscope. They almost always consist of 4x, 10x, 40x and 100x powers. When coupled with a 10x (most common) eyepiece lens, total magnification is 40x (4x times 10x), 100x, 400x and 1000x.

Condenser Lens: The purpose of the condenser lens is to focus the light onto the specimen. Condenser lenses are most useful at the highest powers (400x and above). Microscopes with in-stage condenser lenses render a sharper image than those with no lens (at 400x).

Diaphragm or Iris: Many microscopes have a rotating disk under the stage. This diaphragm has different sized holes and is used to vary the intensity and size of the cone of light that is projected upward into the slide.


Types Of Microscopes

Here are five types of microscopes, their specific qualities, and uses:

Simple Microscope

A simple microscope is simply a large magnifying glass with a shorter focal length that has a convex mirror with a small focal area. The most common examples of this type of device are the handheld lens and eyepiece lens.
When a material is held close to the lens of the microscope, its focus is created, and the original object becomes magnified and more erect. Then, it focuses on a portion of the material by bringing together the two edges of the lens. This creates a smaller, more focused image of the material than the larger area.
Since it’s only a simple microscope, it only has one magnification level depending on what lens is used. Therefore, simple microscopes are only used for reading and magnifying non-complex items. For instance, you can use a magnifying glass to zoom in the details of a map.

Compound Light Microscope

A compound microscope is the most common type of microscope used today, which mechanism is explained earlier. It is basically a microscope that has a lens or a camera on it that has a compound medium in between. This compound medium allows for magnifications in a veWhile the simple microscope only requires natural light to see the object, a compound light microscope needs an illuminator to view the specimen. These are the basic specifications of a compound microscope:

Magnification: This pertains to making the specimen look larger through the microscope through zooming in the lenses. Magnification is a quantified property which ranges from 40x, 100x, 400x, and up to 1000x.

Resolution: This refers to how good the image is captured by the compound microscope lens. A higher resolution means that the image will be clearer and more detailed. Also, it has an improved visual clarity as it has more layers of magnifications.

Contrast: Like in photography, the background’s darkness relative to the focus or specimen is referred to as contrast. Excellent contrast is typically achieved through staining the specimen so its colors would stand out when viewed in the microscope.

Compound microscopes are extremely useful for research on different areas. It has made a big impact on science and technology in general. Some of its popular uses are when viewing a scientific specimen for educational and research purposes. If you’re looking into studying in medical school, you’ll often encounter this type of microscope in your classes.


Stereo Microscope

The stereo microscope, dissecting or stereoscopic microscope, is an optical microscopy version designed specifically for low magnification imaging of a biological specimen. It works through reflecting light off the specimen’s surface rather than transmitted through its medium.
This type of microscope is often used in chemistry laboratories where more detailed, three-dimensional images are required that would be possible with an electron microscope or other high-powered microscope. While the stereo microscopy technology has existed for over 100 years, stereo microscopes only recently have come into being in the laboratory and can produce higher quality images than ever before.
Many people choose stereoscopes over other microscope models because it can produce better quality images depending on one’s needs. In addition, these microscope models require less maintenance and are inexpensive. Stereo microscope applications involve less thorough microscopic requirements, such as viewing manufacturing materials, circuit board work, dissection, and inspection.


Scanning Electron Microscope (SEM)

A scanning electron microscope is a very popular type of scanning electron microscopes, which produces images of a material by scanning the sample with a high-powered beam of electrons. The electrons interacting with atoms within the sample create different signals which contain data about the structure and topography of the material. The images that are produced using these microscope instruments are highly accurate as well as they can be viewed in high resolution using a microscope eyepiece or magnifier.
To obtain appropriate results from an SEM, the sample or specimen should have electrical conduction for the electrons to bounce off on its surface, thus producing a clear image. For the sample to become electrically conductive enough, they’re coated in a thin layer of metals like gold.



You May Like...