what is dark field microscopy and why dark field microscopy?

what is dark field microscopy?

dark field microscopy darkfield technology

tool used to view certain types of translucent samples. The average microscope user may not know about the concept of dark field microscopy, yet it can shed new light on the old way of viewing specimens.
Most people who have survived a biology class know what a light field microscope is. This type of scope uses bright field illumination, meaning it floods the specimen with white light from the condenser without any interference. Thus the specimen shows up as a dark image on a light background (or white field if you will).

This type of unit works best with specimens that have natural color pigments. The samples need to be thick enough to absorb the incoming light; so staining is usually paired with this type of microscope.

Plankton illuminated with a dark field microscopeYet what if the specimen is light colored or translucent, like the plankton on the right? It certainly won’t stand out against a strong white background. Additionally, some specimens are just too thin. They cannot absorb any of the light that passes through them, so they appear invisible to the user. This is where the concept of dark field illumination comes in!

Rather than using direct light from the condenser, one uses an opaque disk to block the light into just a few scattered beams. Now the background is dark, and the sample reflects the light of the beams only. This results in a light colored specimen against a dark background (dark field), perfect for viewing clear or translucent details.

On a grand scale, the same thing happens every day when you look up at the sky. Do the stars disappear when it’s light out? Of course not! They’re still there, their brilliance blotted out by the mid-day sun.

If you’re still having a hard time visualizing this concept, think of a dusty room with the light on and the door open. You may feel the dust affecting your breathing, but you probably won’t see it flying through the air.

Now turn off the light and close the door to just a sliver, while leaving the light on in the adjacent room. If you look at that sliver of light coming through the door, you’ll see all sorts of dust motes suspended in it. You’re employing a similar principle when you use dark field illumination!

dark field microscopy live blood analysis dark field microscopy live blood analysis dark field microscopy live blood analysis

What Advantages and Disadvantages about Dark Field Microscope?

No one system is perfect, and dark field microscopy may or may not appeal to you depending on your needs.

Some advantages of using a dark field microscope are:

Extremely simple to use
Inexpensive to set up (instructions on how to make your own dark field microscope are below)
Very effective in showing the details of live and unstained samples
Some of the disadvantages are:

Limited colors (certain colors will appear, but they’re less accurate and most images will be just black and white)
Images can be difficult to interpret to those unfamiliar with dark field microscopy
Although surface details can be very apparent, the internal details of a specimen often don’t stand out as much with a dark field setup.

Below are contrasting examples of dark field (left) versus bright field (right) illumination of lens tissue paper. Note how they both create a different style of image.

Dark field illumination Bright field illumination

Admit it, by now you’re curious to check out your own dark field! You can create one with minimal time and effort. Just read on.

What is Conclusion about dark field microscope

A dark field microscope can offer brilliant, light images against a dark background of otherwise difficult to view specimens.

Most standard microscopes come with dark field capabilities or accessories to enable this illumination technique.

There are many practical applications of dark field, especially in the field of marine biology, in viewing the many specimens you cannot see using alternative techniques.

However, a researcher must keep in mind the potential issues and limitations that may arise from dark field illumination.

For further information, check out the many microscopy imaging techniques available.

why dark field microscopy?

 

A dark field microscope is ideal for viewing objects that are unstained, transparent and absorb little or no light.

These specimens often have similar refractive indices as their surroundings, making them hard to distinguish with other illumination techniques.

You can use dark field to study marine organisms such as algae and plankton, diatoms, insects, fibers, hairs, yeast and protozoa as well as some minerals and crystals, thin polymers and some ceramics.

You can also use dark field in the research of live bacterium, as well as mounted cells and tissues.

It is more useful in examining external details, such as outlines, edges, grain boundaries and surface defects than internal structure.

Dark field microscopy is often dismissed for more modern observation techniques such as phase contrast and DIC, which provide more accurate, higher contrasted images and can be used to observe a greater number of specimens.

Recently, dark field has regained some of its popularity when combined with other illumination techniques, such as fluorescence, which widens its possible employment in certain fields.

When to Use a Dark Field Microscope

Dark field microscopes are used in a number of different ways to view a variety of specimens that are hard to see in a light field unit. Live bacteria, for example, are best viewed with this type of microscope, as these organisms are very transparent when unstained.

There are multitudes of other ways to use dark field illumination, often when the specimen is clear or translucent. Some examples:

Dark field illumination of caffeine crystalsLiving or lightly stained transparent specimens
Single-celled organisms
Live blood samples
Aquatic environment samples (from seawater to pond water)
Living bacteria
Hay or soil samples
Pollen samples
Certain molecules such as caffeine crystals (right)
Dark field microscopy makes many invisible specimens appear visible. Most of the time the specimens invisible to bright field illumination are living, so you can see how important it is to bring them into view!

 

Contact us.

2 + 4 = ?
anser the questions..

Related Items

  • Product Categories

  • Recent Posts

  • Archives

  • Categories

  • dark field microscopy dark field microscopy analysis dark field microscopy blood dark field microscopy how it works dark field microscopy images dark field microscopy live blood analysis dark field microscopy magnification dark field microscopy pdf dark field microscopy quizlet dark field microscopy ray diagram dark field microscopy resolution dark field microscopy setup dark field microscopy slideshare dark field microscopy syphilis dark field microscopy uk
  • Translate: