Diadema Antillarum Juvenile

This image is a juvenile of the long-spined tropical sea urchin Diadema Antillarum, at day 52. You can see the larvae image from day 32 here.

Image courtesy of Martin Moe.

This image was captured using the Meiji EMZ-13TR stereo zoom microscope along with the Nikon D80 camera adapter.

Microscope Coarse and Fine Focusing

Student microscopes may have coarse focusing only, or both coarse and fine focusing. The National Optical 114-LED microscope is shown below with coarse focusing only. The National Optical 109L microscope is shown below with both coarse and fine focusing. The fine focusing knob makes it easier to really fine-tune the focusing at the higher magnification of 400x.

The coarse focusing knob typically moves either the body tube or the stage up and down. A good quality coarse focus should provide smooth movement. Additionally, it is best to use a microscope with rack and pinion focusing mechanisms. The pinion is a toothed wheel that moves along a grooved bar or "rack" which is attached to the stage or body tube. You can learn more about rack and pinion focusing mechanisms here.

Vorticella

Vorticella is a genus of protozoa, with multiple species. Vorticella live primarily in fresh water streams and ponds. You may be able to locate some in a fresh water stream near your house and look at it under your microscope. Vorticella are most commonly viewed at 400x magnification. Vorticella often stay in clusters, so when looking through the microscope you may notice them grouped together in your field of view. The Protozoan Video, "In the Eye of the Needle" discusses Vorticella in more detail, as well as the Teacher Handbook on Protozoans.

Microscope Eyepiece Inscriptions Explained

You may notice a variety of different inscriptions on microscope eyepieces. This post explains a few of the most common ones.

• WF = widefield
• 10x = magnification (10x magnification)
• 10x/20 = 10x magnification, 20mm field of view. The number found after the magnification usually refers to the eyepiece field of view in mm.
  
• C or K = compensating eyepiece. Some microscope objectives do not correct for chromatic aberration, compensating eyepieces make this correction.
• H = high eyepoint. This is especially helpful for microscope users that wear glasses. High eyepoint means the eye does not need to be as close to the lens on the microscope eyepiece in order to view a clear image.
  

Meiji stereo microscope eyepieces are shown above.

Bee Stinger Images

Finding a dead bee is always a good opportunity to take a look at the insect under the microscope! We used the National Optical DC-128 digital student microscope to view this bee's stinger. It looks rather painful at this magnification!

40x magnification

100x magnification

Metallurgical Microscope for Measuring Plastic Layers

Microscope World recently helped configure a microscope system for a customer who needed to measure the thickness of layers in a very thin piece of plastic (about 0.064mm). The customer wanted a system to perform quality control.

The thin piece of plastic was placed between two slides to hold it vertical beneath the MT7100 metallurgical microscope. The Moticam MC2300 camera was mounted on the trinocular port with a 1.0 c-mount. The microscope magnification was 400x, but because the setup involved a camera with a 1/2" chip and a 1.0 magnification c-mount, the camera's effective magnification was closer to 700-800x.


After capturing the plastic layers image, the Motic Images software (included free with all Moticam cameras) was used to measure each layer of plastic.

This image shows the four different layers of plastic along with their corresponding measurements in microns. The ability to quickly capture an image, make measurements and determine if a layer was the correct thickness allowed this customer to maintain quality control on their production process.

Cleaning Microscope Objectives

In order to determine if your microscope objectives require cleaning, place a blank glass microscope slide under the microscope. With the microscope in focus, move the slide around to determine if any visible spots are staying in place or moving. If the spots are moving they are on the slide. If they stay put, follow the directions below to clean your microscope objectives.

If you are using a dry objective (one that has not been used with immersion oil), you should be able to clean the objective with lens paper or a kimwipe without using any solutions.

If you are using an immersion oil objective, you may have oil hardened on the objective lens, resulting in a sub-par image. Moisten a piece of lens paper with a small amount of distilled water and hold it against the lens to dissolve the oil. If you were using Type B or type A immersion oil you may use Naptha, Xylene or turpentine (only a very small amount on the lens paper). After wiping the oil clean with one of these solvents ensure that the chemicals have been cleaned completely from the objective lens by wiping it again with lens paper using distilled water. We do not recommend using alcohol or acetone as the oil is insoluble to these solvents and they will dissolve most paint and plastics.

Microscope Phase Contrast

Phase contrast is a technique used in microscopy. Phase contrast causes some interference in the light path and enhances microscopy specimens that tend to be the same color as the background they are against. The images below are human cheek cells.

This first image was captured with standard brightfield.

This image was captured using phase contrast.

Notice how when using phase contrast the cells tend to "pop" out of the image. You can even see the nuclei if you look closely at the center of some of the cells. You can learn more about phase contrast here.

Bone Marrow under the Microscope

The following images of bone marrow smears were stained with a modified Wright-Giemsa stain.

Captured at 100x magnification, this image is a bone marrow smear from a patient with chronic myelogenous leukemia.

Captured at 1000x magnification, this image is a bone marrow smear of a myeloma case. You may noticed the binucleated plasmacyte, partly covered by the word "World".

These images were captured using a biological laboratory microscope.

Plan Objectives vs Semi-Plan Objectives

There are typically three types of brightfield microscope objectives that you may encounter.

1. Standard Achromat Objectives
2. Semi-Plan Objectives
3. Plan Objectives

Microscope lenses are curved, resulting in an image that is slightly out of focus at the edges when using a standard achromat objective. An achromat objective guarantees that 60% of the field of view will have a quality flat focus. Semi-plan objectives guarantee a flat field for 80% of the field of view. Plan objectives guarantee 100% and are the best quality objectives.

"Achromat" actually refers to the correcting for color dispersion effects, and you may run across descriptions such as plan achromat objectives or even semi-plan achromat objectives.

Image of frog's blood captured with the Motic BA310 using plan objectives at 1000x magnificaiton. You can learn more about microscope objective lenses here.

Koehler Illumination

Koehler microscope illumination produces illumination on the specimen that is uniform in brightness and free from glare. It is especially helpful when performing photo microscopy. Koehler illumination was first introduced in 1893 by August Kohler, who was working for the Carl Zeiss corporation.

When using Koehler illumination it is important to align the condenser lens for optimal illumination. Here are a few simple steps to follow:

1. Focus on your sample in brightfield mode.
2. Close the field diaphragm (your image will now have a dark cirlce around it and may be slightly out of focus at the edges).
3. Focus the diaphragm so the edges of your image are crisp and sharp, the black circle still remains around the image.
4. Center the image using the two centering screws. (The image with the dark circle around it should now be in the center of your field of view).
5. Open up the field diaphragm again so the entire specimen fills the field of view and the dark circle disappears.

The Motic BA310 microscope is an example of a microscope with Koehler illumination.

Microscope Resolution and Empty Magnification

A common misconception in microscopy is that more magnification is always better. When using a microscope there is a magnification combination of objective + eyepieces that is best for optimal resolution. This ideal magnification can be found using the numerical aperture of the microscope objective.

The formula to find the best microscope objective and eyepiece combination is to take the numerical aperture (NA) and multiply it by 500 to determine the low end magnification and NA x 1000 for the high end magnification. Once you determine the range, then take the objective magnification x eyepiece magnification and if it results in a magnification outside your optical magnification it would be best to use a different eyepiece / objective combination.

The chart below lists common NA values for objectives in the left column. The boxes with the "x" are optimal magnification combinations. For a calculation example let's look at the 40x objective with 20x eyepieces. The 40x NA is 0.65. If we multiply 0.65 x 1000 = 650x. The actual magnification of this combination is 20 (eyepiece) x 40 (objective) = 800x. Since this magnification is outside the optimal magnification of 650x, this is not a good combination for optimal magnification and will result in empty magnification.

Empty magnification is the result of an objective + eyepiece combination that falls outside the realm of optical magnification (see the blue boxes in the chart above). Once magnification rises above the optical magnification there is a bit of added magnification, but the image resolution deteriorates and may almost appear to be out of focus. This is "empty magnification" and will not allow you to view fine details in your specimens.

For more information on microscope resolution click here.

Peacock Feather under Microscope

This image of a peacock feather was captured with the Moticam 2000 camera under a stereo microscope at about 20x magnification.

Microscope Focal Length

A common microscopy term you may hear is focal length. The term focal length refers to the amount of distance required between the objective lens and the top of your object, in order to be able to view an image through the microscope that is in-focus. When using a biological microscope the higher your objective magnification, the shorter the focal length generally is. With the 4x objective there may be some space between the objective lens and your cover slip on your prepared slide. However, when using the 100x objective lens the objective will be almost touching the cover slip, due to a smaller focal length.


You can learn more about focal length as well as finite and infinity corrected optics here.

Cancer under the Microscope

Science has made great progress in fighting cancer. Unfortunately there is still much work to be done. The images below are cancer cells.

Images captured with a Meiji Biological microscope and the MC2000 moticam camera.

Microscope Immersion Oil

When used in light microscopy, oil immersion is a technique used to increase the resolution at higher magnifications. Immersion oil should only be used with oil immersion objectives.

A small drop of immersion oil is placed on top of the cover slip and seals the space between the specimen and the oil immersion objective. When using immersion oil an increase in the numerical aperture is observed, providing increased resolution.

When you are finished using the immersion oil be sure to clean the objective lens to prevent the immersion oil from hardening on the objective.

Polarized Light Microscopy

This is a polarized light image of resorcinol at 400x magnification, courtesy of Mark Simmons. Polarized light microscopy is used primarily to view crystals, minerals, geological specimens and chemicals.

Polarized light microscopy utilizes both a polarizer and an analyzer to provide contrast in specimens. Microscopes with polarization use a polarizer positioned above the light path before the specimen, and an analyzer placed in the optical path between the objective and the eyepiece or camera port. A biological microscope or stereo microscope can have a polarizing kit added on. For advanced polarizing microscopy a polarizing microscope is used.